Question. I can't find a frame filter in any of my WW2 tm's. The only tm that I own showing the frame filter is tm 9-710 from 1953. My track was partially overhauled postwar with the addition of extra pioneer tool fittings. When I added my frame filter, I found the top of the original frame filter and the fasteners attached horizontally (wtf?) to the inside frame, about 4 inches forward of where it's shown in the later tm. So I've installed an nos frame filter, vertically, as in the tm, and so far it's the biggest leaking point. Were the frame filters used during WW2, and is it required, even with the carb filter? I'd love to remove it, but if it's correct to an early track, required, or a good idea to have on, I guess I'll just make new gaskets and apply more teflon.