These mounts were made by Recknagel for Blaser. You can still buy most of the parts today from Recknagel. The exception is the front ring and the barrel-mounted socket. They are custom items specifically for this model. But within this model they interchange. I have 5-6 sets of front rings with barrel -mounted sockets and about 15 rear rings if you need spares. They came from the old Blaser importer Harold Hayes.
Thanks Vol423 for the info. The guy that owned it before me was a little heavy with the screwdriver on these mounts and the screws are pretty bad.
