It looks like some really old fashioned home made hackamore/bit combination. Applying pressure to the nose as well as the mouth. The big metal pieces would help with turning, instead of just the cheek piece on the bit - it has the whole plate to help push the horses head around.
I can't imagine it sitting to well in the horses mouth, and I'm guessing that chain in the bottom photo goes around the chin and hooks up to the other side.
If it was a little better made (different angles etc.) and softer padding, it wouldn't be that harsh of a bit (of course depending on the riders hands)
But yeah - wouldn't put it near any of my horses that's for sure!