Green’s Dictionary of Slang

a con-man who plays a trick of dropping a fake valuable object in the road and offering to let their victim buy it so they can have all the supposed profit.

c.1561		Awdeley Fraternitye of Vacabondes in Viles & Furnivall (1907) 10: A Ryng faller is he that getteth fayre copper rings [...] & walketh vp and down the streetes til he spieth some man of the country, or some other simple body whom he thinketh he may deceaue.
1774		Stamford Mercury 3 Nov. 1/2: Two were convicted of frauds, one of whom was the man, for defrauding a young woman by dropping a ring [...] The ring dropper is to be imprisoned for one year at Newgate.
1781		G. Parker View of Society II 166: The Fawney Rig. A Ring Dropper; a fellow who has gotten a woman’s pocket, with a pair of scissors, some thread, a thimble, and a housewife with a ring in it, which he drops for some credulous person to pick up. [...] He then comes the stale story of ‘If you will give me eight or nine shillings for my share, you shall have the whole.’ If you accede to this and swallow his bait, you have the ring and pocket, worth a bout sixpence.
1786		Derby Mercury 31 Aug. 1/2: He had been decoyed by a Ring-Dropper in expectation of sharing in the good Fortune of finding a Cluster Diamond Ring, value 150l.
1797		Sporting Mag. Mar. IX 315/2: Notorious characters, as low gamblers, ring droppers, sharpers, and thieves of every description.
1808		G. Andrewes A Stranger’s Guide or Frauds of London 21: Ring-Dropper [...] are a sort of cheats who [...] most commonly exercise their villainous arts upon a young woman. Their method is privately to drop a ring just before such persons come up etc.
1803		Morn. Post (London) 12 Sept. 3/4: He was sneeringly called Mahafft the ring-dropper, because he sold pinchbeck rings.
1819		Chester Chron. 29 Jan. 3/5: These were noble sentiments [...] sentiments to which every smasher, trapper, kidlayer, ring-dropper [...] and forger of bank-notes present, would heartily subscribe .
1821		‘An Amateur’ Real Life in London I 556: Your ring-droppers, or practisers of the fawney rig, are more cunning in their manoeuvres to turn their wares into the ready blunt.
1831		Morn. Post (London) 4 Nov. 3/4: Chain-Dropping [...] Henry Turley, a most infamous and successful ring-dropper was apprehended [...] He had just dropped a purse containing a chain and seals worth about eighteen-pence, from which he bargained to receive three pounds from his intended dupe.
1836		A. Thornton Don Juan in London II 240: You will see a specimen of two more of our grades, the Ring Dropper and the Money Dropper, one in a velveteen jacket, the other in corduroy.
1843–44		Dickens Martin Chuzzlewit (1995) 578: Nor did it mark him out as the prey of ring-droppers, pea and thimble-riggers, duffers, touters, or any of those bloodless sharpers, who are, perhaps, a little better known to the Police.
1859		G.A. Sala Twice Round the Clock 153: We have plenty of rogues in our body corporate yet. [...] We are not free from skittlesharps, card-cheats, ‘duffers,’ and ring-droppers.
1863		T. Taylor Ticket-Of-Leave Man Act II: I shouldn’t wonder if it was some nasty ring-dropper.
1877		Graphic 29 Sept. 18/3: One of the oldest dodges of the street swindler is to drop a ‘duffing’ ring made in imitation of old jewellery. This trick was successfully practised [...] in Oxford Street [...] the ring-dropper is now in custody.
1882		Eddowe’s Jrnl 11 Jan. 3/6: He had reason to believe that the prisoner was a ‘ring dropper’.
1902		Hull Dly Mail 24 June 6/1: The prisoner merely lived upon his wits, and was known [...] as a professional ring-dropper. [...] He passed off brass rings worth probably 4d each on farm lads [...] as gold for £2.
1917		Western Mail 15 June 4/4: A man [...] trespassing on the great Western station was described as a ‘ring-dropper’.
1921		Nottingham Eve. Post 10 June 1/5: [headline] Nottingham Man Duped by ‘Ring Dropper’.