The original mould used to make Britain's stamps is expected to raise £10,000 at auction this week.
The plaster cast, which was designed in 1967, has been used to print over 320 billion stamps over the past 40 years.
The Queen is said to like the design so much, that she declined to have it updated - unlike her effigy on the British coin.
The cast, by renowned sculptor Arnold Machin, is generating excitement among stamp collectors across the nation.
"Nothing like this has come up for sale before, it is so rare," said a member of staff at the Staffordshire auction house where it's to go under the hammer.