Green’s Dictionary of Slang

drop game n.

1. [mid-19C+] (UK Und., also drop trick) a confidence trick whereby the victim is persuaded to pay money for a wallet, ring or some valuable, supposedly found on the ground but actually planted by the con man.

2. [late 19C] in gambling, a trick whereby a gambler substitutes a note of higher value than that which was apparently bet, then reveals its worth and demands to be paid the correspondingly greater winnings.

In compounds

drop gamester (n.)

[mid-19C] (US Und.) a confidence trickster who performs the drop game.