Green’s Dictionary of Slang

(orig. RAF) useless.

1945		C.H. Ward-Jackson It’s a Piece of Cake (2nd edn) 61: U/S. Unserviceable. It is normally applied to inanimate objects but colloquially to animate ones as well. Thus, ‘I’m in dock. I’m afraid I shall be u/s for some time.’.
1953		K. Williams Diaries 13 Jan. 86: The first shots were U.S. because the film buckled, so we had to shoot all over again.
1959		W. Hall Long and the Short and the Tall Act I: I’d like to put the boot on the burk who dished us out with a u/s batt.
1998		I. Welsh Filth 16: Worth fuck all, totally u.s.