Green’s Dictionary of Slang

(UK/Aus. milit.) white wine.

1918		Aussie (France) VII Sept. 8/1: We went to an Estaminet to celebrate the great occasion, and ordered a bottle of ‘point blank’ and I drank his health and he drank my health. [Ibid.] Dec. 3/2: The proceeds were to be used to buy beer or ‘point blank’ for all members.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words.
1930		(con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier.