Buccaneer,
The scope on your rifle although similar in appearance to the WA5, WB5, WB3 etc is in fact a model known simply as the Winchester 8x. The following text is reproduced from "Old Rifle Scopes" authored by Nick Strobel. ISBN 0-87341-830-1
Quote "In 1939 Winchester introduced an 8x scope specifically for its model 75 target rifle.This scope is unmarked except for an 8x on the objective bell and has a characteristic japaned brass tube that gives a greenish-black colour to the tube finish. The stamped sheet metal mounts are marked "Winchester". The last listing I have for the 8x is in the 1944 Gun Digest" End quote.
Winchester 8x (1939 - 1945)
Magnification - 8x.
Field of view - Not given.
Luminosity - Not given.
Eye relief - Not given.
Length - Approx 18". (Roughly 450mm in new money).
Weight - Not given.
Tube diameter - 0.750" (Roughly 18mm in new money).
Cheers,
Simon.