Green’s Dictionary of Slang

(UK Und.) a rogue who specializes in dropping something supposedly valuable where it will be found by a potential victim, who is either lured into a game or persuaded to buy the ‘valuable’, while the conman claims that although they should, by rights, share the profits, he will sell his share and let the victim have the whole benefit; alternatively the victim is introduced to some of the sharp’s friends, who propose a game of cards or dice, in which they rob him.

1669		Nicker Nicked in Harleian Misc. II (1809) 108: There come in shoals of hectors, trepanners, [...] bulkers, droppers.
1674		C. Cotton Compleat Gamester 6: Shoals of Huffs, Hectors, Setters, Gilts, Pads, Biters, Divers, Lifters, Filers, Budgies, Droppers, Crossbyters, etc., and these may all pass under the general and common appellation of Rooks.
1693		Poor Robin [as cit. 1669] .
c.1698		B.E. Dict. Canting Crew n.p.: Gold-droppers, Sweeteners, Cheats, Sharpers.
1725		New Canting Dict. [as cit. c.1698].
[1735		Proceedings Old Bailey 2 July 88/1: The Prisoner has been a Gambler [...] for several Years past. [...] A Gambler is one of the Modern Cant Names for a Money Dropper].
1748		Smollett Roderick Random (1979) 73: This polite, honest, friendly, humane person, who had treated us so civilly, was no other than a rascally money-dropper.
1753		J. Poulter Discoveries (1774) 31: There are generally four Persons concerned; that is, the Sailor, called a Legg Cull, to pinch the Nobb; the next is the Capper, who always keeps with the Sailor; and two Pickers up, or Money Droppers, to bring in Flats.
1762		G.A. Stevens in Adventures of a Speculist (1788) II 101: Blue Manchester velvets [...] are generally the uniform of Bum-bailiffs, Sleight-of-hand-men, and Money-droppers.
1770		R. King Frauds of London 53: Money-Droppers [...] generally ply at the most public places in town, and also at fairs and country markets. [...] The Dropper [...] lays down a guinea, or other piece of money, close to the countryman, then, in a voice of exultation, exclaims, I have found a guinea.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Gold droppers, sharpers who drop a piece of gold, which they pick up in the presence of one unexperienced person for whom the trap is laid; this they pretend to have found, and as they saw them pick it up, they invite him to a publick house to partake of it, when here, two or three of their comrogues drop in, as if by accident, and propose cards or some other game, when they seldom fail of stripping their prey.
c.1786		Grose Classical Dict. of the Vulgar Tongue ms. additions n.p.: Money Droppers. Cheats who drop money, which they pretend to find just before some country lad; and by way of giving him a share of their good luck, entice him into a public house, where they and their confederates cheat or rob him of what money he has about him.
1788		Grose Classical Dict. of the Vulgar Tongue (2nd edn) n.p: [as 1786].
1795		A Fortnight’s Ramble through London 39: The mob now were proposing to duck the two droppers in an adjoining pond in the Long-fields, but Jack swore he would prosecute them. [Ibid.] 42: I threw one of the five pieces on the table, which the money-dropper had recently given me.
1796		Grose Classical Dict. of the Vulgar Tongue (3rd edn) [as cit. 1788].
1808		G. Andrewes A Stranger’s Guide or Frauds of London 20: Money-Droppers [...] ply at the most public places in town [...] The dropping of money is the lure to inveigle countrymen into their company.
1811		Lex. Balatronicum [as cits. 1785, 1788].
1818		W. Perry London Guide 69: money-droppers [...] It is an almost obsolete practice; and its twin, ring-dropping, is not less disused [...] ‘What is this this?’ says the dropper; ‘my wiggy! if this is not a leather purse with money!’.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue [as cits. 1785, 1788].
1846		N.Y. Herald 28 May 2/4: [headline] Arrest of a ‘Dropper’.
1851		Tarboro Press (NC) 22 Feb. 1/5: he also belonged to a gang of thieves, pick-pockets and pocket-book droppers.
1862		E. de la Bédollière Londres et les Anglais 315/1: gold droppers.
1871		Galaxy (N.Y.) Mar. 191: When we know that the ‘pocket-book dropper’ yet decoys the money even of the city-bred by his stale device; that the ‘gift enterprises,’ ‘envelope game,’ and similar threadbare tricks yet serve to attain the ends of the sharpers.
1927		(con. 1890s–1900s) H. Asbury Gangs of N.Y. 261: A dropper was a thief who dropped a wallet filled with bad money at the heels of a victim and then pretended to find it. Pleading that he was in a great hurry, the thief induced the sucker to purchase the wallet with the avowed intention of finding the rightful owner.