Katie -
I know little to nothing about Hasselblad equipment. The mounting ring is a bayonet mount, has the number 63 on it - is there a bay63 lens? - the filter holder part is that silver piece at the front - it unscrews and would hold an unthreaded 63mm diameter filter (probably hold a series VIII as well). I'm sure there are members who know all types of stuff about Hasselblad (this was in a box of miscellaneous equipment that I'm trying to help a friend move out - I can ask him tomorrow, but I doubt if he'll remember - he sold his Hasselblad outfit quite a few years ago).
Kris