Essen, Germany  - A German stamp collector who 20 years ago mislaid one of the world's most valuable stamps, a "Post Office" Mauritius One Penny Red, is to offer it for sale next week.

There are thought to be only 15 of the stamps in existence and they are only exceeded in value by the legendary matching Two Pence Blue, of which only 12 are believed to survive.

Worried that a burglar would seize it, Ullrich Schulze hid the Red, which he had inherited from his father, in an album full of almost worthless German stamps and then forgot the hiding place.

For 20 years, philatelists described the specimen and the card it is on as the "limbo" Red, perhaps never to be seen again.

But while looking for something completely different, Schulze stumbled on the treasure again.

At an auction on May 8 in a ballroom of Essen's Hugenpoet Palace Hotel, bidding for the Red is to open at 200,000 euros (265,000 dollars).

The stamp is from the first series issued on the island of Mauritius and is distinguished by the legend "Post Office," instead of the words "Post Paid," as printed on later Mauritius stamps.

Some of the world's top collectors are expected to attend the sale, organized by the Dr Wilhelm Derichs auction house of Cologne.

The catalogue suggests the next owner can be confident that their name will enter philatelic history, and auctioneer Roland Meiners expects several German business tycoons to attend.

All present are expected to wear evening dress and champagne will be served afterwards.

Meiners confesses he will be a touch tense as he takes the first bids in Germany for any Mauritius "Post Office" stamps for 24 years.

The stamp on sale has an unusual history all its own. The present owner's father, Gerhard Schulze, who had made his fortune from vending machines, deadlocked with the previous vendor in the 1970s over the price.

In the end the two agreed to barter instead, and Schulze senior paid for the stamp with a 40-foot motor yacht.

Mauritius stamps are perhaps the most coveted items a philatelist can acquire. The Two Pence "Post Office" generally changes hands for a million dollars or more. Several of the "Post Office" series are no longer on the market, having been acquired by public museums.

The primitively printed stamps went on sale in September 1847 and many were used to send invitations to a ball hosted by the island's governor. The wording on Mauritius stamps was altered the next year, 1848. (dpa)