Premium/Discount Tracker — Methodology

1. What this tracker measures

For each tokenized precious-metal product, we compute the percentage gap between its on-chain market price and the equivalent LBMA / LPPM spot fix for the underlying metal at the same point in time.

• Premium (positive %) — token trades above spot. Buyer pays more than the underlying metal would cost on the wholesale market.
• Discount (negative %) — token trades below spot. Buyer pays less, but this often reflects redemption frictions, liquidity gaps, or counterparty risk premia.
• Zero — token trades at parity with spot. Rare in practice.

2. Premium / discount formula

Where:

• token_price_usd — token price in USD at the time of the metal fix (gold 15:00 London, silver 12:00 London), taken from CoinGecko hourly prices (aggregated across CEX/DEX venues). This applies to all six tokens, PAXG included.
• oz_per_token — troy ounces of physical metal backing one token. See denominations table below.
• spot_lbma — LBMA Gold PM Fix or LPPM Silver Fix of the same date as the token price, in USD per troy ounce (London auction).

3. Tokens tracked & denominations

Denomination constants used in code

G_PER_OZ = 31.1034768   # troy ounce in grams (NIST)
KAU oz_per_token = 1 / G_PER_OZ = 0.03215074656...

4. Spot reference (LBMA / LPPM)

Same-day rule: each token price is compared only with the fix of the same date. London auctions publish twice daily for gold (AM and PM fix) and once daily for silver.

Weekends and London bank holidays: no new fix is published, so the chart has no point for that day. An older fix is never carried forward.

5. Primary data sources

6. Update cadence

• Token prices — refreshed daily alongside LBMA spot and ETF closes.
• Spot fixes — refreshed daily from prices.lbma.org.uk JSON.
• 365-day history — rolling window. Old days drop off the chart automatically as new days append.
• Files — /data/gmri/tokens-current.json (snapshot) and /data/gmri/tokens-history.json (daily series). Raw JSON is public.

7. Arbitrage calculator

The calculator on the main tracker page applies the same spot reference to a hypothetical position.

The fee input lets the user model exchange fees, custody fees, or expected slippage. The calculator does not include: gas costs on chain, FX conversion, redemption fees charged by the issuer, or capital-gains tax. Treat the output as a ceiling, not a realised result.

8. Limits & caveats

• Asynchronous fixes. LBMA publishes once or twice daily. Token markets trade 24/7. A 3% gap measured on a Sunday is partly the absence of a new fix, not a real dislocation.
• CoinGecko aggregation. Token prices are volume-weighted across venues. Thin tokens (XAGM, KAG) can show jumps that reflect one large trade, not a market-wide move.
• Fix-time rule. The token price and the metal fix refer to the same moment. Until 3 November 2026 the token price was taken at 00:00 UTC, about 15 hours before the gold fix; on fast-moving days this created false premiums (example: XAUT on 30 January 2026, +9.23% at 00:00 UTC against +0.59% at the 15:00 fix time).
• History since 4 November 2025. The free CoinGecko API serves hourly prices for the past 365 days only, so earlier days cannot be recomputed at the fix time. The older points (24 June – 3 November 2025, 00:00 UTC method) are kept in tokens-history-legacy-0000utc.json and are not shown on the chart.
• Liquidity rule. A day is left out when the token’s 24h volume on CoinGecko falls below 5% of its median over the previous 30 days — a sign that the main market is missing from the feed. Example: KAG on 21, 24 and 25 August 2026, when its CoinGecko volume fell far below normal. Excluded dates are listed in tokens-history.json.
• Spike rule. A day is left out when one token moves more than 8% and moves back more than 8% the next day, while the metal fix moved less than 3%. Examples in the current history: KAG on 20 May 2026 and KAU on 30 June 2026. Excluded dates are listed in tokens-history.json.
• Custody quality is not measured here. A token trading at parity with spot is not automatically safer than one at a 5% discount. Attestation cadence, auditor reputation, jurisdiction, and redemption rights matter and are not in this premium number.
• We do not include wrapper ETFs. Backed bGOLD, 21Shares physical gold ETPs, etc. are tracked on the GMRI™ comparison index, not here.
• Survivorship. Tokens that delist or lose CoinGecko coverage drop out. Historical premium series may not be reconstructable from this site alone for retired tokens.
• No backfill. If a fetch fails, we do not interpolate. The chart shows a gap until the next successful fetch.

9. Change log

3 November 2026 — fix-time rule

The token price is now taken at the time of the metal fix (gold 15:00 London, silver 12:00 London) instead of 00:00 UTC. History recomputed from 4 November 2025; older points archived. PAXG also moved from CF Benchmarks PAXGUSD_RR (published at 16:00 London) to the CoinGecko price at 15:00 London, so all six tokens are compared at the same minute.

2 November 2026 — same-day rule and liquidity rule

Fix view and history now compare only prices of the same date; no fix (weekends, London holidays) means no point. Days with a CoinGecko volume gap and one-day token-only price spikes are left out. PGOLD (removed 18 August 2026, unverified denomination) is no longer listed. Live spot is labelled as CME futures quotes via Yahoo Finance.

23 June 2026 — v1.0 initial release

Launched Premium/Discount Tracker with 5 gold tokens (PAXG, XAUT, KAU, XAUM, PGOLD) and 2 silver tokens (KAG, XAGM). 365-day rolling history. Daily refresh alongside LBMA spot and ETF closes.

23 June 2026 — LBMA spot 365-day window

Extended LBMA / LPPM history fetch from latest-only to a rolling 365-day window so the comparison chart shows a full year of context, not a single snapshot.

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Premiums are calculated by TrueSource Metals™. Token market data: Powered by CoinGecko.