Ashtead philatelists are preparing to sell a defective three penny stamp for more than £160 at an auction this weekend.

The purple stamp, which was printed in 1961 to celebrate the centenary of the Post Office Savings Bank, would have cost someone three pence 55 years ago.

Paul Warren, one of the owners of Epsom Stamp Shop in Waterloo Road, Epsom, says the stamp would normally not fetch more than a few pence.

But one eagle-eyed buyer noticed the stamp was missing its brown colouring, making it extremely rare, and therefore valuable, according to Mr Warren.

He believes it may sell for more than £160 when it goes under the hammer on Saturday, July 2.

Mr Warren has speculated that two sheets of 120 stamps might have got stuck together before going through the printing press – meaning one sheet did not receive the brown colouring that the other 114 million otherwise identical stamps did.

He added: “These things do happen, but it is a very rare item.

“Some of these stamps would have been used in the post, others would have been destroyed.

“It also could easily have been used without being noticed.

“It is obviously a very big premium on what it would be in a normal collection.”

The auction will be held at St George’s Christian Centre in Barnett Wood Lane, Ashtead, on Saturday, July 2. For a catalogue, or for more information, call 01372 720051, or email info@epsomstamp.co.uk.