Green’s Dictionary of Slang

(Aus./N.Z.) a quart bottle of beer, esp. a quart of draught beer in a square-faced gin bottle.

1910		N.Z. Truth 22 jan. 7/1: When [Constable[ Roach entered he found a ‘square rigger’ of beer [...] One of the other men in the shop parted up the money for the ‘rigger’.
1916		N.Z. Truth 7 Oct. 6/2: He had arranged to get a ‘rigger’ of beer if the other gentlemen would follow suit.
1929		N.Z. Truth 14 Nov. 8/3: I had got some liquor earlier, a rigger of beer.
1941		F. Sargeson ‘That Summer’ in Coll. Stories (1965) 156: I’d always buy a couple of riggers and he’d buy some buns.
1942		Sydney Morn. Herald 11 May 5/7: Riggers holding an imperial quart have been increased in price.
1988		McGill Dict. of Kiwi Sl. 92/2: rigger quart of beer, precursor of the halfgallon jar; short for ‘squarerigger’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].