Here you go, needs batteries apparently.
(Description a VHS video cassette with slot on the top to fit a Betamax tape, lid is open )
View attachment 167006
That is a VHS C adaptor. Early camcorders had a mini version of a VHS mechanism that could taKe tapes with 30 or 45 minutes worth of tape. The adaptor enabled the tape to load into a full size mechanism by pulling the tape loop out so that it could be threaded around the full sized drum for playback of camera footage.
The Beta system was totally different in that:
the tape feed to the drum followed a large 'U' path
the drum was larger so the angle across the drum surface was more shallow
the linear speed was slower
the chroma and luminance carrier frequencies were different
so not much chance of interchangeability there by any practical means.