Green’s Dictionary of Slang

fawney adj.

(US und.) of jewelry, watches, etc., faked for use in a cifidence trick .

Eldridge & Watts Our Rival, the Rascal 220: [T]he ‘confidence man’ will vary his performance by pulling out of his pocket what is known to his craft as a ‘fawny’ watch, a gift, as he will pretend, from his dear, old father [...] If the trick succeeds, the dupe will get an oroide watch of the poorest kind, and the confidence man will get away with the money.