What's in the lot, and what to pay

• Open a listing on Marktplaats, 2dehands, eBay, Catawiki, Delcampe, Vinted, Kleinanzeigen and Leboncoin and click the Coin Spotter icon. Other sites work too, once you allow them.
• The side panel shows the photos and warns about the listing: ships from outside your customs area, from China or Hong Kong, no returns.
• The verdict compares the target total with the asking price plus shipping and import charges.
• Right-click any image, paste a screenshot or drop photos to scan those instead.

• At a coin fair, in a shop, or at home: take up to 10 photos, or pick them from the gallery. Photograph both sides, or a whole tray at once.
• Add what the seller asks, and what they claim. Claims are checked against the photos, never taken on trust.
• Earlier scans stay on the phone with their photos, so you can come back and check prices later.

Country, ruler, denomination, year and mint mark, catalogue number, metal, a grade estimate, and any authenticity concern, with a cut-out from the photo.

A target price (about the lower middle of recent sales for that grade) and a range. With silver and gold prices per gram in the settings, precious-metal coins show their melt value and never price below it.

Check market price searches the web for recent sales of one coin and replaces the estimate. Numista and eBay sold searches are a tap away, and the list exports as CSV.

1. Build it
   From the Archivist-Spotter repository, with Node 22: npm install, then npm run build.
2. Load it
   Open chrome://extensions, switch on Developer mode, click Load unpacked and pick the apps/extension/dist folder.
3. Add your key
   Open the extension's settings, choose Gemini or Claude, paste your key and press Test key.

1. Build the APK
   In apps/android: npx eas-cli build --platform android --profile preview. Expo's build service makes the APK; it needs a free Expo account.
2. Install it
   Open the download link on the phone and allow installing from that source.
3. Add your key
   Open Settings from the first screen, choose Gemini or Claude, paste your key and press Test key.

Create a key at aistudio.google.com/apikey. Without billing it runs on the free tier: no charge, but rate-limited, and Google may use what you send to improve its products. A Google AI Pro or Ultra subscription doesn't cover API keys.

Get a key at console.anthropic.com. You pay per use; Coin Spotter shows the expected cost before a scan and the actual cost after.

Only to the provider you chose, straight from your browser or phone. Keys stay on your device. The privacy page has the details.