Green’s Dictionary of Slang

(UK Und.) any ring containing a gemstone, esp. a diamond, thus Polari groinage, jewelry.

1914		Gloucs. Echo 25 Feb. 6/5: In thieves’ backslang [sic] ‘white horse ’ means silver goods, ‘red lot’ gold goods, ‘elephants’ diamonds [...] and ‘groney’ ring .
1930		(con. 1910–20s) D. Mackenzie Hell’s Kitchen 119: Groins ... rings.
1934		P. Allingham Cheapjack 190: Take sights. Screw th’ donah’s groinies.
1935		Thieves Slang ms list from District Police Training Centre, Ryton-on-Dunsmore, Warwicks 5: Grawney: Ring [ibid.] Groins: Rings.
1954		J. Phelan Tramp at Anchor 110: Men who were not burglars nevertheless habitually used words like [...] groin, when they meant [...] ring.
1959		J. Gosling Ghost Squad 25: Thieves’ argot, spoken properly, is a foreign language which needs to be learned [...] a diamond is a ‘groin’ (don't ask me why !).
1977		D. Powis Signs of Crime 186: Groin/groyne A ring with some form of stone in it.
1989		in G. Tremlett Little Legs 12: Your little white box, in which you may have a nice groin (a ring).
2019		P. Baker Fabulosa 293/1: groin, groyne a ring.
2023		R. Milward Man-Eating Typewriter 109: [They] donned drogles, bombshell shykas and sparkling groinage.