Green’s Dictionary of Slang

contraries n.

[such dice are ‘contrary’ to those currently in play]

any form of false or legitimate dice, to be brought into and withdrawn from a game as the cheater desires.

[UK]G. Walker Detection of Vyle and Detestable Use of Dice Play in Judges (1926) 43: If ye lack contraries, to crossbite him withal, I shall lend you a pair of the same size that his cheats be.
[UK]Grose Classical Dict. of the Vulgar Tongue n.p.: The names of false dice: A bale of bard cinque deuces A bale of flat cinque deuces A bale of flat sice aces A bale of bard cater traes A bale of flat cater traes A bale of fulhams A bale of light graniers A bale of langrets contrary to the ventage A bale of gordes, with as many highmen as lowmen, for passage A bale of demies A bale of long dice for even and odd A bale of bristles A bale of direct contraries.
[UK]Lex. Balatronicum.