It's a slosh-over filter, I think it's missing the top cover/ring. There was a perforated ring that went on top of the lower part (shown on agitator) that caught larger bits of lint, strings, etc. and smaller holes in the lower section for finer lint. They also made this for the automatics, similar design and color. Largely a gimmick, but they could advertise the feature just like many others of the time.
I have one of each breed, but have tried it in the automatic and it did little more than to impede rollover.