I've "inherited" this thing a long time ago, and I have no idea what it is. It consists of a cylindrical porcelain bowl with the words "Mason Cash England" stamped in the bottom, a very sturdy cast-iron frame with a screw through and two circular discs of zinc-plated iron that fit neatly inside. I could half imagine it being use to produce a perfectly circular burger, but it seems like absurd overkill. Here's a couple of pictures:
What is it actually for - anything to do with cookery at all?