I'm not exactly sure about all its pieces but it allows the 3PT arms to be used to lift the front mounted snowblower. I don't have it but some of the parts that came with my B2660 blower are for it and the instructions mention its installation. I've seen it work at a dealer long ago. If you use this method, then you cannot have an implement on the 3pt because you'll drop the implement each time you lower the blower.
Any good luck with the broken case? How are the manuals working for you?
-Peter