Wow! These are so so rare i had only ever heard of them before this. What you have here is a super dooper mount for brushed dmc cranks. They are supposedly hard to get going but once started reach 88mph easily. They bolt on to a plate with 17 m10 bolts which then bolts on to that mount. The titanium copper mix makes them rust free and you can have a 6t cog if you wished.
Was it expensive?