Green’s Dictionary of Slang

ring dropping n.

1. a swindle whereby some valuable object is dropped in the road, where it is found by a potential victim. This leads to an encounter, after which the victim is either lured into a fixed game or, in the case of the (fake) valuable, persuaded by the trickster to buy it, claiming that while they should share the profits, he, the con-man, will sell his share and let the victim have the whole benefit; also attrib.

[UK]Hereford Jrnl 24 Oct. 3/4: The stale trick of ring-dropping was practised very successfully.
[UK]Scots Mag. July 355/2: The following is a list of the crimes committed by prisoners who were in Newgate from Sept. 28 1785 to Sept. 28 1786 [...] Ring-dropping 2.
[UK]P. Colquhoun Police of the Metropolis 135: When those depraved people [...] find that any of the tricks which they have practised for a certain length of time become stale, (such as pricking the belt for a wager, or dropping the ring,) they abandon them.
[UK]Bury & Norwich Post 15 Nov. 2/3: A fraudulent trick, somewhat similar to the London art of Ring-dropping, was attempted.
[UK]‘An Amateur’ Real Life in London I 553–4: The practices of ring and money dropping have, at various times, been carried on with great success, and to the serious injury of the unsuspecting. The persons who generally apply themselves to this species of cheating are gamblers, who ingeniously contrive, by dropping a purse or a ring, to draw in some customer with a view to induce him to play.
Cork Constit. 16 Nov. 4/5: When a duffer, or ring-dropping cheat, / Brings trash, and a flat gulls to buy it, he / Only displays for the rhino / Something of ‘over anxiety’ (to avoid a pecuniary loss).
[UK]A. Thornton Don Juan in London II 408: One lived the ring-dropping, the other was a duffer.
[UK]Bell’s New Wkly Messenger 12 Apr. 6/2: The French rogues beat the English rogues all to nothing. The cleverest trick of ring-dropping, or fobbing, sinks into insignificance before the roguery (called the Vol a l’Americaine).
Leicester Mercury 1 Mar. 1/2: The prisoner King had, by the well-known offence of ‘ring-dropping,’ imposed uon several persons.
[UK](con. 1840s–50s) H. Mayhew London Labour and London Poor I 351/2: According to another informant, the ring-dropping ‘lurk’ is now carried on this way.
[UK]Sl. Dict. 270: Ringdropping is a pursuit to which London ‘magsmen’ and ‘street-muggers’ are prone. A ring or other spurious article is supposed to be found just in front of a ‘soft-looking party,’ and he or she is tempted to buy it at less than half its supposed value.
[UK]W. Hooe Sharping London 36: Ring-Dropping, the trick of dropping a ring or other article of jewellery within sight of any likely flat with the object of selling it as gold.
[UK]Globe (London) 8 Oct. 5/5: A further charge [...] of attempts to steal by means of the ‘ring-dropping’ trick, to which they pleaed guilty.
[UK]Nottingham Eve. Post 18 Jan. 3/3: Bridget Murphy, an old woman [...] was charged [...] with attempted larceny by a trick known as ring-dropping.
Hendon & Finchley Times 3 Mar. 5/4: He was dealt with under the Probation Act for the ring-dropping trick.
[UK]F.D. Sharpe Sharpe of the Flying Squad 279: Ring Dropping used to be a popular sport.

2. a term of scorn, ‘equivalent to “tell your grandmother to suck eggs”’ (Ware); so common had sense 1 become that anyone could spot a ring-f.

[UK]rJ. Ware Passing Eng. of the Victorian Era.