A banknote from the Seychelles in which the word "sex" was secretly hidden in the design is to be sold at auction.
The 50 Rupee note issued between 1968 and 1973 features the Queen and within the palm trees by her head is the naughty message.
Some believe the insult was added because at the time the Seychelles was trying to gain independence from Britain.
It has been suggested that it was done by a rogue engraver who tweaked the original design of the currency.
There are also those who believe it was just an unfortunate error; however, another note in the series appears to carry the word "scum", implying it was deliberate.
Today 50 Rupees is worth about £2.50 but the note that is to go under the hammer at Duke's of Dorchester in Dorset on October 15 has an estimate of £200.
Timothy Medhurst, from the saleroom, said: "This is a very collectable item for obvious reasons.
"Amazingly the added message wasn't noticed - or was perhaps never mentioned - until after it stopped being printed.
"There are various theories about how the word came to be included. Many think the engraver Brian Fox of Bradbury & Wilkinson, the printers, put it in.
"It is an otherwise attractive note but would have disappeared into obscurity if it had not been for its secret message.
"Collectors are always keen to have one and this is in good condition and was consigned by a collector.
"It is part of our October sale which will see a huge variety of notes, coins, medals and other related items go under the hammer."