Green’s Dictionary of Slang

a middle-man who places stolen goods or counterfeit money with a purchaser.

1959		J. Gosling Ghost Squad 63: It was no use picking up the stall-holder who was passing the coins — he was only one of many ‘placers’.
1970		‘Metropolitan Police Sl.’ in P. Laurie Scotland Yard (1972) 326: placer, a: an underworld wholesaler in stolen goods, a broker.
1977		G.F. Newman Villain’s Tale 13: ‘In nice safe used notes that you don’t have to go again on,’ Lynn said. ‘How bad’s that? No problem spending them when you want. No hungry placer taking the the lion’s share.’.