There was enormous excitement in the lead up to the sale of the Karpov collection of Belgian stamps at David Feldman in November, and frenetic bidding resulted in exceptional prices and records on the day.

In particular, a beautiful green invert stamp is now the most valuable stamp to sell from the Belgian Congo.

But there was a particular story behind one of the lots. Whilst a conscientious stamp collector such as Anatoly Karpov will be at pains to preserve the stamps and covers in their collection, it is unusual for them to be improved. But in one case this is exactly what happened, thanks to a certain Mr P.

This was lot number 30102 in the sale: This was a Nieuport letter (January 1851) for Boulogne-sur-Mer in France featuring carmine-rose 40C stamps in two strips of five, a band of six and a single cancelled by the '87' postmark .

The cover is believed to be the largest of the 40 cents postage, and the stamps are attractive with nice margins too, so it shouldn't be a big surprise that it had spent time in another great collection before Karpov's: the Burrus collection.

The Burrus-Karpov cover, restored with the help of Mr P

However, when the Burrus collection was sold in 1963 the single stamp was missing.

When the item came up for auction once more in 2000, a certain French collector known as Mr. P, studied the auction catalogue and found in his pages of used Medaillon stamps, a 40c single with the exact same "87″cancel.

 Inspired by the belief that it might be the missing stamp, he went to Brussels for the auction. Before it took place, he examined the cover carefully and even secretly placed his stamp in the missing spot revealing a perfect match.

This couldn't possibly be a coincidence, as this cover is probably the only place where these 40c stamps are united with these cancels. Mr P attended the auction and with great enthusiasm bid for the cover without revealing his discovery.

Sadly for him, the competition was intense, and he was outbid in the sale by Anatoly Karpov. Mr. P did not wish his discovery to be lost to the philatelic world, so he contacted Karpov and the philatelic gem was rendered complete once more.

In the 2011 sale it quadrupled its estimate of €15,000 to sell for €70,000 ($91,000).