Green’s Dictionary of Slang

no bloody good.

1917		‘You’re Only a P.B.O.’ in C.H. Ward-Jackson Airman’s Song Book (1945) 38: When you get in the old machine to start on a damned O.P. / You cover yourself with tons of clothes and they’re all of them N.B.G.
1924		(con. WWI) A.G. Pretty Gloss. Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: n.b.g. No bloody good.
1930		E. Waugh Vile Bodies 91: ‘N.B.G. in fact, eh? Then that goes there.’ She put the slip into the wastepaper basket.
1937		G.D.H. & M. Cole Brothers Sackville 161: I suppose it’s like most of my ideas: N.B.G.
1947		J.L. Riordan ‘Some ‘G.I. Alphabet Soup’’ in AS XXII:2 Apr. 111: Though most personnel employ profanity freely, some prefer softer expressions like N.B.G. (’no blankety good’)9 [9. This may, however, derive from the British slang phrase ‘no bloody good’].
1968		Orlando Sentinel (FL) 2 May 23/4: N.B.G. means no bloody good.
2003		McGill Reed Dict. of N.Z. Sl.