Quick answer
Track coin collection value by logging acquisition prices, pulling realised auction data monthly, and charting portfolio value on a single dashboard. MyCoinage does this automatically with hourly updates; spreadsheet-based tracking needs a manual monthly refresh from Spink, Baldwin's, or Noonans catalogues.
TL;DR
- Portfolio value = sum of current realised-price estimates across all coins at their current grades
- Never use asking prices, only realised sales
- Refresh cadence matters: hourly is ideal, monthly is minimum
- Separate bullion value (spot-driven) from numismatic value (auction-driven)
- Track against cost basis to see total return, not just current value
Table of contents
- What "value" means for a coin collection
- The two components: bullion and numismatic
- Data sources that actually work
- Refresh cadence
- Charting the portfolio
- Return calculations
- Common questions
- FAQ
What "value" means for a coin collection
There are four plausible values for any coin, and they're usually different numbers.
| Value type | Definition | Use case |
|---|---|---|
| Retail replacement | What a dealer charges | Insurance high-water mark |
| Realised auction | Recent hammer + BP | True market value |
| Dealer buyback | What a dealer pays | Quick-liquidation floor |
| Melt / bullion | Metal content only | Absolute floor for precious metals |
For portfolio tracking, realised auction price is the honest figure. It's what a coin actually fetches when offered to a willing market. Retail is optimistic; buyback is pessimistic.
The headline number
When someone asks "what's your collection worth?" the defensible answer is: sum of realised-price estimates at current grades. That's the same basis insurers use for claim assessments and HMRC uses for IHT valuation.
The two components: bullion and numismatic
Every coin has both a bullion value and (sometimes) a numismatic premium. A 1oz gold Britannia is worth spot plus a small premium. A 1887 proof sovereign is worth spot plus a large premium. A worn 1920 silver half-crown might trade below spot because silver's recovery costs matter.
Bullion tracking
Bullion value = metal weight × fineness × spot price. Spot moves daily; a sovereign's 7.32g of 22ct gold (so 7.32 × 0.9167 = 6.71g fine) fluctuates with the London fix. MyCoinage's metals page pulls live spot for gold, silver, platinum, palladium and copper, hourly.
Numismatic tracking
Numismatic premium = realised auction price minus bullion value. This is where the money is in rare coins. The numismatic premium on a rare 1933 penny (see 1933 penny value) can be five figures above the penny's trivial metal content.
Data sources that actually work
Three sources give reliable realised-price data for British coins:
Spink auction archive. The gold standard. Hammer prices plus buyer's premium, multiple sales per year for most major denominations, searchable back to the 1990s. Paid subscription but worth it for serious collectors.
Baldwin's and Noonans. Complementary to Spink. Noonans (formerly DNW) in particular handles a lot of mid-range material. Both publish results online free; older results sometimes paywalled.
Completed eBay transactions. Useful for mid-market pieces where auction houses don't sell many. Filter for "Sold" listings only. Beware of shill bidding and private treaty sales reported as auctions.
MyCoinage's coin_prices database combines all three plus PCGS certified-sale records into a single grade-level aggregate. Free tier users see the aggregate; Pro users see the individual sale records.
Sources that don't work
- Active listings on eBay, Vinted, Facebook Marketplace
- "Price guides" that haven't been updated in 5+ years
- Community-submitted "market values" without source verification
- Dealer stock prices (retail markup inflates the figure)
Refresh cadence
How often should you update values?
| Collection size | Manual refresh | Automated refresh |
|---|---|---|
| Under 25 coins | Quarterly | Daily (free tier MyCoinage) |
| 25-100 coins | Monthly | Hourly (Pro tier) |
| 100+ coins | Weekly | Hourly |
| £50k+ value | Daily | Hourly + alerts |
Manual refresh at the required cadence for a 100-coin collection is roughly 3-4 hours per month. Automated is zero. That's one major reason collectors migrate from spreadsheets to apps, the price-keeping time compounds.
Charting the portfolio
Value over time is only meaningful as a chart. A single value today tells you nothing; a chart showing £42k in Jan 2024, £48k in Jan 2025, £51k in Jan 2026 tells you a story.
What to chart
- Total portfolio value, monthly snapshots
- Bullion component versus numismatic component
- Cost basis versus current value (the gap is unrealised gain)
- Top 10 holdings by current value
- Sector breakdown (sovereigns, crowns, pennies, etc.)
MyCoinage's dashboard uses ECharts 5 and shows all of these on a single page. For spreadsheet users, a pivot chart refreshed monthly does the same job with more elbow grease.
Time horizons
- Monthly snapshots for active tracking
- Annual snapshots for IHT planning (HMRC wants Dec 31 valuations)
- Ad-hoc snapshots before any major purchase, know what you're adding to
Return calculations
Three useful returns:
Total return since acquisition. (current value − cost basis) / cost basis. A sovereign bought for £250 now worth £320 = 28% total return.
Annualised return. Total return adjusted for holding period. Two sovereigns, both 28% total, but one held 2 years (≈13% annualised) and the other held 8 years (≈3% annualised), very different stories.
Return versus spot. For bullion, compare collection return to pure spot return. If gold spot rose 15% and your sovereign holdings rose 18%, the numismatic premium is expanding. If spot rose 15% and your sovereigns rose 12%, premium is compressing, the market's less keen on numismatic sovereigns.
When to realise
This is personal, but some rules of thumb:
- Sell bullion premiums when they spike above historical norms (Britannia premiums above 15% of spot are high)
- Hold rare numismatic pieces, the premium tends to grow with scarcity
- Trim duplicates when one grade becomes notably undervalued relative to another
See are old coins worth anything for identifying what's in the collection in the first place.
Common questions
How do I value a coin nobody has sold recently?
Estimate from comparables. A 1894 sovereign with no recent sale records can be valued from adjacent years (1893 and 1895) and grade-adjacent results. Apps do this automatically; spreadsheet users triangulate manually.
Does currency matter?
For UK collections priced in GBP, no, unless you hold US or European pieces. MyCoinage's currency switcher converts the whole dashboard to USD, EUR or GBP live, using hourly FX rates.
Should I track realised sales as they happen or catalogue-only?
Both. Your own realised sales are the most reliable data point for your collection specifically. Catalogue-wide data covers gaps.
How do I handle a coin with wildly swinging realised prices?
Use a rolling 12-month median instead of the last sale. A single outlier sale (an aggressive bidder, a poorly-attended auction) shouldn't anchor your valuation.
FAQ
Q: What's the difference between portfolio value and insurance value?
A: Portfolio value uses realised auction prices (what you'd get selling). Insurance value uses retail replacement (what you'd pay to replace). Insurance value is usually 20-35% higher.
Q: Should I include coins I've lent out?
A: Yes, flagged as "on loan". They're still yours.
Q: How often do the leaders on the MyCoinage leaderboard rebalance?
A: Hourly. See the leaderboard for live standings.
Q: Does Pro tier change the price data I see?
A: Pro shows individual sale records and the alert feature. Free tier shows aggregated grade averages, same data source.
Q: What about VAT on investment coins?
A: UK investment gold coins (sovereigns, Britannias) are VAT-exempt. Silver and non-investment gold attract 20% VAT on the premium. Bake this into cost basis carefully.