Your scabbard is an unaltered M7 with the body made out of resin impregnated cotton duck and these were made between 1943-53. You can see the yellowish material showing through the green paint near the tip. You can tell its not a cut down M3 as you can see the small cut outs in the body under the scabbard throat. If it were a cut down the body would meet flush with the throat.
http://www.thegca.org/pdfs/Bayonets409.pdf has some good info on this. I think I read on one of the bayo points that the B / N number under the lip of the throat possibly indicates 1940's construction with the 1950's marked V / P and that 1950's had a more light (yellowish) shade of green on the scabbard body.
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