Green’s Dictionary of Slang

1. (US) a dollar [SE washer, a small metal disk].

1908		B. Fisher A. Mutt in Blackbeard Compilation (1977) 150: I simply got to get that 25 washers back before I face my squaw.
1912		Ade Knocking the Neighbors 6: When they got together 100 of these Washers, a man in New York would let them have some Tiffany Water of Rare Vintage.
1919		A. Baer Two & Three 18 May [synd. col.] Fifty washers for a seat at the Willard-Dempsey tussel [sic] ain’t so bad.
1920		A. Baer War Memorials 1 Sept. [synd. col.] One addle pateriot wants to spend a billion washers for another Tower of Babble.
1972		B. Rodgers Queens’ Vernacular 137: Coins: [...] washers (some prison usage).

2. (US gay) a condom [its being placed between two surfaces to relieve friction].

1972		B. Rodgers Queens’ Vernacular.
1988		H. Max Gay (S)language.