Yes it is a James ML (Military Lightweight) but it is an immediate postwar model. James continued to make the ML after the WWII and it sold very well. In fact the majority of ML were made immediately post war in the 46-48 period. The postwar models were more or less identical regardless of the year of manufacture so it is very difficult to say exactly what year it is.
They are very popular and quite a few survive although not in such good original condition as yours.
Cheers,
