An 18th century biscuit made to commemorate the philanthropy of a set of conjoined twins is to be sold at auction.

Biddenden Cakes were rectangular hard biscuits moulded with an image of Mary and Eliza Chulkhurst, known as the Biddenden Maids.

The twins were born in the village of Biddenden in Kent in 1100 and lived until the age of 34.

Tradition has it that when one of the twins died the other refused to be separated from her twin, saying ‘As we came together we will go together’, and died six hours later.

The sisters are reputed to have bequeathed land to the village, known as the Bread and Cheese Lands, the rent from which was used to pay an annual dole of food and drink to the poor at Easter.

Since at least 1775 the dole included Biddenden Cakes, bearing the effigy of the conjoined maids.

The earliest biscuits made are thought to have been marked only Biddenden, like the example being sold at Dominic Winter Auctioneers in South Cerney, Gloucestershire, on January 21, with a guide price of between £100 and £150.

Later versions of the 8.5cm by 5.3cm biscuit show the names of the twins and their date of birth and age at death.

Other Biddenden Cakes can be found in the Pitt Rivers Museum in Oxford and the Wellcome Collection in London.

Auctioneer Chris Albury said: “We’ve sold quite a few pieces of wedding cake from the Charles and Diana wedding of 1981 for as much as £1,000 and we are no strangers to selling quirky collectables.

“A couple of years ago we sold an 18th century gingerbread hornbook mould for £3,200, and we’ve sold a lot of items relating to the celebrated conjoined twins Chang and Eng, but this quite literally takes the biscuit.

“There was a lot of consultation and debate among the valuation team and while we are more experienced at dating paper items, pictures and antique objects, we were all quite certain that this was antiquarian and possibly pre-Victorian.

“Certainly, the deceased vendor among whose effects this was recently found was an 18th century specialist, which tended to back up our hunch.

“The Biddenden lettering seems to conform to these earlier examples too, and commemorative examples of more recent vintage I have now seen pictures of do look more obviously fresh and perhaps a little more appetising.

“Our specimen seems to have reached a totally stable condition physically and is unlikely to deteriorate further if kept away from heat and damp.

“That said, anyone thinking of bidding £100 plus to then eat it would be crackers.”