The Easiest Way to Get Silver Dec 2025 (SIZ25) - Per Troy Ounce Historical Rates (REST API example)

If you need Silver Dec 2025 (SIZ25) historical rates per troy ounce to backfill charts, audit pricing decisions, or run signals for a trading model, the fastest path is to query the Metals-API Historical and Time-Series endpoints with SIZ25 as your symbol. In this guide, we’ll show you exactly how to pull daily silver futures prices for December 2025 delivery, parse the JSON, handle weekends/holidays, and store the results safely for analytics, ERP valuation, or e-commerce pricing engines.

Why Silver Dec 2025 (SIZ25) historical data matters for developers

SIZ25 represents a specific delivery month in the silver futures curve. For developers building trading tools, pricing engines, or analytics pipelines:

• Backtesting strategies: You need consistent, per troy ounce historical data to compute signals and compare against spot or other maturities.
• Portfolio and ERP valuation: Procurement teams and manufacturers price forward inventory exposure using near- and far-month contracts.
• Smart manufacturing and supply chain: Production scheduling benefits from forward-looking inputs and sensitivity analysis tied to the silver futures term structure.
• Digital market analysis: Align inventory, e-commerce SKUs, and payment quotes with current and historical contract values.

With Metals-API, you can retrieve SIZ25 daily closes historically, fetch an OHLC snapshot for a given date, and compile a clean time series for your models—all in a standard, developer-friendly JSON format.

What you’ll build with Metals-API

We’ll walk through three core tasks using the SIZ25 symbol:

• Historical point lookup: Retrieve the SIZ25 rate for a known date.
• Time-series extraction: Pull a date range (e.g., Sep–Dec 2025) to power charts and backtests.
• Daily OHLC: Fetch open, high, low, close for a target date to support candlestick charts and analytics.

We’ll use only a handful of endpoints relevant to SIZ25. For the full API surface, see the Metals-API Documentation. To confirm symbol availability and naming, visit the Metals-API Supported Symbols list. When you’re ready, get your free key on the Metals-API Website.

Key concepts before you query SIZ25

• Units: Metals-API returns metal rates “per troy ounce” by default. A troy ounce is ~31.1034768 grams, not the same as an avoirdupois ounce.
• Base currency: By default, rates are relative to USD. You can set base to other currency codes if supported (e.g., base=EUR). If you keep base=USD, rates are “metal units per USD” or “USD per troy ounce” depending on the rate convention in your response. See the “unit” and “base” fields to interpret values.
• Timestamp and date: Responses typically include a Unix timestamp and an ISO date (e.g., 2025-12-01). Use the date as the trading day marker and the timestamp for cache/versioning.
• Weekends/holidays: Futures don’t trade every calendar day. Time series may skip non-trading dates, or the rate may be carried from the previous session, depending on market convention and data availability. Always programmatically handle gaps.

Confirming the SIZ25 symbol

Before writing code, verify the symbol on the symbols endpoint. Use the curated list on the Metals-API Supported Symbols page to confirm futures-contract naming for silver December 2025. Contract codes frequently mirror industry conventions (for example, SIZ25 for COMEX Silver Dec 2025), but always confirm to avoid mismatches.

Endpoint 1: Historical Rates for SIZ25 (single date)

Use this when you need a single day’s historical value—e.g., for a month-end valuation or to backfill a missing point in your database.

Purpose and functionality

The Historical endpoint returns rates for a specific date in YYYY-MM-DD. You’ll receive a JSON payload containing “base”, “date”, and a “rates” object keyed by symbol—here, SIZ25—and a “unit” string. This is ideal for deterministic point lookups and precise reconciliation tasks.

Request parameters

• access_key: Your API key (required). Get one from the Metals-API Website.
• base: Reference currency (e.g., USD). If omitted, defaults to USD.
• symbols: Comma-separated list of symbols to retrieve. For this guide: SIZ25.

Example: curl request for a single historical date

curl -s "https://metals-api.com/api/2025-12-01?access_key=YOUR_API_KEY&base=USD&symbols=SIZ25"

Example JSON response (historical day)

{
"success": true,
"timestamp": 1764547200,
"base": "USD",
"date": "2025-12-01",
"rates": {
"SIZ25": 0.0386
},
"unit": "per troy ounce"
}

Field-by-field interpretation

• success: Boolean indicating request success.
• timestamp: Unix epoch (seconds). Use it to version your cache or reconcile with other datasets.
• base: Currency for the quoted rate. Default is USD; if base is USD, interpret rates as the quantity of the instrument per USD or as a reciprocal depending on the dataset’s convention. Use the combination of base and unit to understand the price orientation.
• date: ISO trading date for the returned data.
• rates: Object keyed by symbol (SIZ25). The value is the numerical rate associated with the base and unit.
• unit: “per troy ounce” clarifies the metal quantity basis in the denominator.

Real-world use cases

• Audit: Verify the official close for SIZ25 on a specific business day and reconcile P&L.
• Valuation: Price inventory or purchase orders using the month-end SIZ25 mark.
• Chart backfill: Patch a missing candle for a one-off date without re-fetching the entire range.

Common pitfalls and troubleshooting

• Non-trading days: If the target date is a weekend or holiday, ensure your logic either requests the previous business day or handles an unchanged close. Consider a pre-check for business days to avoid repeated missed hits.
• Symbol mismatch: If you mistakenly query an invalid contract code, the rates object may be empty or not include SIZ25. Always validate against the Supported Symbols catalog.
• Base currency confusion: Persist the base and unit along with the rate in your database. This prevents downstream confusion when mixing datasets.

Performance considerations

• Caching: Cache by date+symbol+base. Historical points don’t change frequently; caching dramatically reduces redundant calls.
• Batching: If your use case needs multiple symbols or adjacent dates, prefer the Time-Series endpoint for efficiency.

Endpoint 2: Time-Series for SIZ25 (date ranges)

Use this to pull a continuous historical range for SIZ25—for charting, factor models, moving averages, and seasonality studies.

Purpose and functionality

The Time-Series endpoint returns a daily “rates” object per date in your requested range. You control the start_date and end_date, and can request one or more symbols. For SIZ25, you’ll typically query a window around the December 2025 delivery month, such as September through December.

Request parameters

• access_key: Your key.
• base: e.g., USD.
• start_date: Start of interval, inclusive (YYYY-MM-DD).
• end_date: End of interval, inclusive (YYYY-MM-DD).
• symbols: SIZ25 (or multiple symbols separated by commas, if supported for your plan).

Example: curl request for Q4 2025 time series

curl -s "https://metals-api.com/api/timeseries?access_key=YOUR_API_KEY&base=USD&start_date=2025-09-01&end_date=2025-12-31&symbols=SIZ25"

Example JSON response (time series subset)

{
"success": true,
"timeseries": true,
"start_date": "2025-09-01",
"end_date": "2025-12-31",
"base": "USD",
"rates": {
"2025-09-01": {
"SIZ25": 0.0391
},
"2025-09-02": {
"SIZ25": 0.0390
},
"2025-09-03": {
"SIZ25": 0.0392
},
"2025-12-01": {
"SIZ25": 0.0386
},
"2025-12-02": {
"SIZ25": 0.0387
}
},
"unit": "per troy ounce"
}

How to consume and store the series

• Primary keys: Combine date+symbol. Persist base and unit as columns to keep lineage.
• Missing dates: Do not assume calendar continuity. If a date is absent, it may be a non-trading day. For analytics that require continuity, forward-fill with caution and always tag imputed values.
• Timezone: Use the “date” keys (UTC-based ISO) as your canonical trading day; store timestamped ingestion metadata separately.

Use cases

• Charting (candles and lines): Plot SIZ25 daily closes over the quarter.
• Backtesting: Compute moving averages (e.g., 20D/50D), momentum, or reversion signals specific to the December 2025 contract.
• Manufacturing planning: Simulate input cost scenarios across the quarter to adjust production schedules or procurement timing.

Performance and scaling tips

• Chunking: For longer histories, split into monthly or quarterly ranges and parallelize with care. Respect request quotas and consider exponential backoff on retries.
• Compression: If your stack supports gzip, enable it to reduce payload size.
• Storage: Use columnar storage (e.g., Parquet) for analytical workloads and time-partitioning for efficient queries.

Endpoint 3: OHLC for SIZ25 (per date)

When you need richer daily bar data for a given date (for example, to render a candle or compute intraday-informed analytics), use the OHLC endpoint for that specific trading day.

Request parameters

• access_key: Your key.
• base: e.g., USD.
• symbols: SIZ25.
• date: This endpoint is structured as /open-high-low-close/YYYY-MM-DD.

Example: curl request for a target date

curl -s "https://metals-api.com/api/open-high-low-close/2025-12-01?access_key=YOUR_API_KEY&base=USD&symbols=SIZ25"

Example JSON response (OHLC)

{
"success": true,
"timestamp": 1764547200,
"base": "USD",
"date": "2025-12-01",
"rates": {
"SIZ25": {
"open": 0.0387,
"high": 0.0389,
"low": 0.0385,
"close": 0.0386
}
},
"unit": "per troy ounce"
}

Field interpretations and best practices

• open/high/low/close: Standard OHLC values for the date. Store as decimals with adequate precision.
• Consistency checks: Ensure close in OHLC aligns with the historical endpoint’s close for the same date where applicable.
• Candles and indicators: Use these fields to render candles and compute ATR, intraday ranges, and volatility screens for SIZ25.

Complete request-to-analysis flow in JavaScript

The following example fetches a SIZ25 time series and computes a simple 10-day moving average on the close. It assumes you treat the time-series “rate” as the closing value for each date. Replace YOUR_API_KEY with your actual key from the Metals-API Website.

/**
* Fetch SIZ25 daily rates for a range and compute a 10D moving average.
* Notes:
* - Returns an array of { date, close, ma10 }.
* - Assumes the daily rate represents the close for that date.
*/
async function fetchSIZ25Series(start, end, base = 'USD') {
const url = new URL('https://metals-api.com/api/timeseries');
url.searchParams.set('access_key', 'YOUR_API_KEY');
url.searchParams.set('base', base);
url.searchParams.set('start_date', start);
url.searchParams.set('end_date', end);
url.searchParams.set('symbols', 'SIZ25');

const res = await fetch(url.toString(), { headers: { 'Accept': 'application/json' } });
if (!res.ok) {
throw new Error('Network response was not ok: ' + res.status);
}
const json = await res.json();
if (!json.success || !json.rates) {
throw new Error('API returned an error or empty rates payload');
}

const entries = Object.keys(json.rates)
.sort() // ISO dates sort lexicographically
.map(d => {
const rate = json.rates[d] && json.rates[d]['SIZ25'];
return rate ? { date: d, close: rate } : null;
})
.filter(Boolean);

// Compute 10D moving average
const window = [];
const out = [];
for (const row of entries) {
window.push(row.close);
if (window.length > 10) window.shift();
const ma10 = window.reduce((a, b) => a + b, 0) / window.length;
out.push({ date: row.date, close: row.close, ma10 });
}
return { base: json.base, unit: json.unit, series: out };
}

// Example usage:
fetchSIZ25Series('2025-09-01', '2025-12-31')
.then(({ base, unit, series }) => {
console.log('Base:', base, 'Unit:', unit);
console.table(series.slice(-10));
})
.catch(err => console.error(err));

What the code does

• Builds a time-series query for SIZ25 with a specified date range.
• Sorts ISO date keys and extracts the SIZ25 rate as the daily close.
• Computes a rolling 10-day moving average for downstream analytics and visualization.

Interpreting values, units, and conversions

Metals-API responses include a “unit” field, which for SIZ25 indicates “per troy ounce”. Be explicit about unit semantics in your application:

• Troy ounces to grams: If your ERP or BOM is gram-based, convert by multiplying troy ounces by 31.1034768.
• Base currency: Keep “base” alongside each time series in storage. If you later join with EUR-based series, you will need to reconcile currencies first.
• Numeric precision: Store decimals at sufficient precision (e.g., 6–8+ places) to avoid rounding artifacts in signals and charts.

Caching, retries, and weekend logic

• Immutable history: Cache historical and time-series responses keyed by the full request (base, symbols, start/end dates). Expire sparingly.
• Rate smoothing: If your chart requires continuous calendars, forward-fill weekends/holidays for visualization only, while keeping the underlying raw series intact for calculations.
• Retries: Use bounded retries with exponential backoff and jitter. Maintain idempotency by hashing the request URL.

Data quality checks for SIZ25

• Contract roll awareness: If you are analyzing the curve or stitching contracts, ensure you don’t accidentally mix SIZ25 with another month. Keep symbol granularity.
• OHLC vs. close: If you combine OHLC and single-rate historical endpoints, verify that the close aligns within expected tolerances for the same date.
• Outliers: Programmatically screen for spikes or gaps due to limited-session anomalies; annotate rather than delete.

Security and key management

• API key storage: Keep your Metals-API key in a secrets manager or environment variable, not in source control.
• Client vs server: For server-rendered apps, call Metals-API from your backend when feasible to keep keys private.
• Least privilege: Rotate keys periodically and monitor request patterns for anomalies.

Silver and modern manufacturing: why SIZ25 fits digital supply chains

Silver’s unique conductivity and antimicrobial properties make it critical in electronics, photovoltaics, and medical devices. For smart manufacturing, aligning raw material plans with the futures curve—like SIZ25—enables:

• Just-in-time procurement: Time purchases around favorable forward pricing windows.
• Scenario planning: Stress-test margins using time-series data for SIZ25 rather than spot proxies.
• IoT-driven cost control: Feed SIZ25 historicals into MES/ERP for dynamic cost-of-goods sold forecasts.

For industry background and contract details, you can also consult the exchange’s contract specifications (for example, see CME Group Silver futures specs) alongside your Metals-API integration.

Architecture patterns for SIZ25 ingestion

• Batch loader: Nightly job pulls the previous day’s SIZ25 historical or OHLC and appends to a warehouse table keyed on date+symbol+base.
• On-demand microservice: A small service fetches SIZ25 time slices for UI-driven date pickers and caches in Redis.
• Hybrid: Use the Time-Series endpoint for initial backfill and the Historical/OHLC endpoints for daily deltas.

Data validation and sanitization

• Schema enforcement: Validate presence of success, date, base, and unit. Confirm SIZ25 exists in the rates object.
• Type checks: Parse numbers as decimals/floats and guard against NaN.
• Domain constraints: Reject negative or zero prices as invalid; log and quarantine suspicious rows.

Concrete cURL and JSON walkthrough for SIZ25

1) Historical endpoint for a mid-December date

curl -s "https://metals-api.com/api/2025-12-15?access_key=YOUR_API_KEY&base=USD&symbols=SIZ25"

{
"success": true,
"timestamp": 1765756800,
"base": "USD",
"date": "2025-12-15",
"rates": {
"SIZ25": 0.0384
},
"unit": "per troy ounce"
}

2) Time-Series endpoint around delivery

curl -s "https://metals-api.com/api/timeseries?access_key=YOUR_API_KEY&base=USD&start_date=2025-11-15&end_date=2025-12-20&symbols=SIZ25"

{
"success": true,
"timeseries": true,
"start_date": "2025-11-15",
"end_date": "2025-12-20",
"base": "USD",
"rates": {
"2025-11-17": { "SIZ25": 0.0389 },
"2025-11-18": { "SIZ25": 0.0388 },
"2025-11-19": { "SIZ25": 0.0387 },
"2025-12-01": { "SIZ25": 0.0386 },
"2025-12-02": { "SIZ25": 0.0387 },
"2025-12-03": { "SIZ25": 0.0386 },
"2025-12-04": { "SIZ25": 0.0385 },
"2025-12-05": { "SIZ25": 0.0386 }
},
"unit": "per troy ounce"
}

3) OHLC endpoint for a single day (candlestick)

curl -s "https://metals-api.com/api/open-high-low-close/2025-12-05?access_key=YOUR_API_KEY&base=USD&symbols=SIZ25"

{
"success": true,
"timestamp": 1764902400,
"base": "USD",
"date": "2025-12-05",
"rates": {
"SIZ25": {
"open": 0.0386,
"high": 0.0388,
"low": 0.0385,
"close": 0.0386
}
},
"unit": "per troy ounce"
}

Field usage in applications

• success: Split pipeline paths early—if false, log, retry, or alert.
• timestamp: Attach to data lineage; correlate with other ingestion timestamps.
• date: Primary time index for charting and analytics.
• base: Tag to prevent inadvertent currency mixing.
• rates.SIZ25: Your key numeric series for SIZ25; treat as the daily close for historical/time-series responses unless you explicitly use OHLC.
• unit: Display on charts/tables (“USD per troy ounce” context). Maintain auditing fidelity.

Practical production tips a beginner might miss

• Numeric formats: Always parse numbers using locale-agnostic routines; don’t rely on string concatenation with default locales.
• Resilience: Add guard rails for empty “rates” objects or partial payloads on low-liquidity/holiday periods.
• Backfills vs daily deltas: Keep two paths—(1) bulk backfill with Time-Series and (2) daily append with Historical/OHLC.
• Schema migrations: If you add more fields later (e.g., high/low), use additive migrations to preserve existing queries.

Advanced analysis examples with SIZ25

• Term-structure alignment: Join SIZ25 with other delivery months (e.g., SIU25, SIH26 if supported) to compute calendar spreads; keep contract-specific series separate prior to spread calculation.
• Risk and hedging: Engineers can integrate SIZ25 series into Monte Carlo simulations for procurement timing and margin protection.
• Manufacturing tech: Introduce SIZ25 price triggers to IoT-driven reorder points—activate purchase orders when prices breach thresholds relative to moving average bands.

Observability and governance

• Dashboards: Monitor API call success rates, latency, and cache hit ratio. Alert on anomalies.
• Data contracts: Document assumptions (base currency, unit, close definition) and propagate via data catalogs.
• Reproducibility: Version your backtests by data snapshot date/time and API timestamp.

Getting started: obtain your key and confirm SIZ25

• Step 1: Visit the Metals-API Website and get a free API key.
• Step 2: Verify SIZ25 availability and naming on the Supported Symbols page.
• Step 3: Start with a small Time-Series request, then persist the data into your preferred store (SQL, data lake, analytics engine).

FAQ

• What unit does SIZ25 use?
  Responses specify “per troy ounce.” If you need grams, multiply by 31.1034768.
• What about non-trading days?
  Expect gaps in the time-series on weekends/holidays. Don’t assume daily calendar continuity. Forward-fill only for visualization and label imputed values.
• How do I change the base currency from USD?
  Pass base=<CURRENCY_CODE> in your request if supported. Always store the base with your series to avoid mixing currencies downstream.
• Can I get candlestick data for a specific SIZ25 date?
  Yes, use the OHLC endpoint with the date path and symbols=SIZ25 to retrieve open, high, low, and close.
• Where do I find all available symbols?
  Use the Metals-API Supported Symbols catalog to validate symbol names like SIZ25.
• Where is the full API reference?
  See the Metals-API Documentation for complete details, including authentication and advanced features.

Conclusion

For developers who need accurate Silver Dec 2025 (SIZ25) historical rates per troy ounce, Metals-API offers a streamlined path: use Historical for one-off dates, Time-Series for ranges, and OHLC when you need full daily bars. Persist “base” and “unit” alongside values, handle weekend gaps and contract specifics, and cache aggressively to minimize redundant requests. With a concise JSON schema and reliable endpoints, you can integrate SIZ25 into trading models, manufacturing cost analytics, and real-time pricing tools efficiently.

Get started now: grab a free API key from the Metals-API Website, confirm SIZ25 on the Supported Symbols page, and implement the requests shown above. For deeper capabilities and endpoint options, explore the complete Metals-API Documentation. For contract background, you may also review CME Silver futures specifications as a complement to your API-driven workflow.