M31 Feldflashen is a early one with date 39, prewar could be, or war time production who knows. It .8 L canteen which is standard. Germans also made 1L canteens.
It not a fully matched set because the Cup would also be marked WAL 39.
Ive seen WAL maker before, however i dont know what the firm name is.
Good canteen regardless
If you look one ebay, orig cups will come up from time to time, just got to keep your eye out. Some dealers might have them.