Luck penny

a small sum given back for luck to one who pays money.

See also: Luck

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
Fortune suddenly smiled upon Jo, and dropped a good luck penny in her path.
Bad enough the farmer had bought the ponies in the first place but when he asked for a luck penny to seal the deal the sly dealer dumped the donkey on him.
They will be presented in blue or pink pouches inside a teddy bear card with the message: "Solid sterling silver good luck penny."
Even on that character-making night when the bidding came within a 'luck penny' of the magic figure, O'Brien had the backbone to put the horse back in the van and bring him home to Cork.
The man who bought the Vauxhall paid pounds 400 cash and handed Mr Dowey a pounds 20 note, describing it as a "luck penny".
To add to the couple's bad luck Penny's brother died suddenly in August and Linda stepped in to take Graham to the funeral as the cortege cars could not take wheelchairs.