Green’s Dictionary of Slang

(Aus.) us used in games of two-up, a double-headed coin.

1919

Mirror (Sydney) 31 Aug. 8/2: When Scott was searched the sergeant found on him four double-headed and one double-tailed pennies. The other three fellows were among the mugs, although before the ‘nobs’ and ‘shieler,’ as the coins are termed in the vernacular, were unearthed, they probably would have declared that they knew all about the tricks of the game.