Green’s Dictionary of Slang

1. (UK Und.) describing the size of a gang of criminals, which can be two-, three-, four-handed etc; thus mob-handed under mob n.² ; team-handed under team n.; also used of any group, e.g. police.

1865		Leaves from Diary of Celebrated Burglar 40/1: As for myself, I don’t mean to ‘graft’ four-handed.
1903		Coventry Eve. Teleg. 29 Dec. 2/7: It was a three to one chance against me; they were three-handed.
1937		E.H. Sutherland Professional Thief in Hamilton (1952) 110: A four-handed mob packs in for the day.
1950		Goldin et al. DAUL 90/1: Handed. (Always preceded by, and hyphenated with, a numerical adjective, as two-handed, five-handed, etc.) Has reference to the number of people involved in an act.
1962		R. Cook Crust on its Uppers 47: he sees old cocked-hat-and-whiskers climbing out of a motor three-handed.
1974		G.F. Newman You Flash Bastard 241: The firm that had blagged the safe deposits had been four-handed, and had entered the bank perfectly respectably.

2. equipped.

2001

K. Sampson Outlaws (ms.) 8: Out jumps this little firm, hired in and that, tool-handed, proper mob and that.