Trading duplicates: how exchange actually works

Guides · 9 September 2026

Every collection produces duplicates, and duplicates are the only currency in collecting that costs nothing to acquire. Trading them is how gaps get filled without money – but it only works if the other side can see what you have and trust how you describe it. Both of those are preparation problems, not negotiation problems.

Preparing duplicates so they are tradable

1. Separate them physically. A duplicates box is not the collection; keeping them mixed guarantees you trade away the better copy by accident.
2. Identify them. An unidentified duplicate is worth nothing in exchange because the other side has to do the work. Country, year and catalogue number, using the method in the guide to identifying an old stamp.
3. List them. The same fields as your main catalogue, with condition noted – the structure in the guide to cataloguing a collection. A list can be sent; a shoebox cannot.
4. Photograph the ones that matter. Both sides, even light, no cropping, following the guide to photographing a collection.

What makes an exchange fair

• Compare states, not just catalogue numbers. The same issue in different condition is not the same trade, as set out in the guide to coin condition and its stamp equivalent.
• Count completeness. A full short set is worth more than the sum of its parts, and splitting it to balance a trade destroys what made it worth trading.
• Value need over rarity. Fair means both sides fill a gap. An item nobody needs is not made valuable by a catalogue line.
• Say when you are unsure. "I think this is the perforation 12 variety but I have not measured it" is a stronger position than a confident guess that turns out wrong.

Describing condition honestly

The fastest way to end a trading relationship is a description that flatters. Note thins, hinge marks, folds, scratches, cleaning and repairs before sending – every one of them will be found by the person who receives it, and repairs in particular show under raking light exactly as described in the guide to repair and restoration. A declared fault costs nothing; a discovered one costs the whole relationship.

Packing so the trade survives the post

1. Stamps in glassine or inert sleeves, never loose in a folded sheet of paper.
2. Coins in individual holders, never touching, wrapped so they cannot move inside the packet.
3. Paper items flat between stiff card, never rolled or folded to fit an envelope.
4. Nothing in soft PVC, for the reasons in the guide to storing coins and metal.
5. Include your list with the parcel, so the other side can check what arrived against what was agreed.

Etiquette that gets you a second trade

• Send when you said you would, and say when you have sent.
• Confirm arrival, even when everything is fine – silence reads as dissatisfaction.
• Raise a problem immediately, with photographs, rather than after weeks.
• Offer the fix you would want: replacement, return, or a credit against the next exchange.
• Keep a record of who you traded with and what moved, as provenance for both sides – the reasoning in the guide to provenance.

Knowing what you actually need

Trading works only when the gaps are visible, which is why an album with empty spaces beats a full one, as in the guide to arranging an album. A reference catalogue makes the same point at a larger scale: the open archive holds 80,472 stamp images from 271 countries and territories, 855 coins, 635 banknotes and 3,332 badges, which is enough to see what a series contains before deciding what to ask for.

Open the sections: stamps, coins and banknotes, badges.