Re: Stevens 416 US Training Rifle
The blocks you are looking at are for a long tube target scope. These are standardized, and the "eyebrow" cut you refer to designate a rimfire application. The rings they fit are found on Unertl, Lyman target spot, Redfield 3200, Flecker, Davis optical.....ect.. All these now somewhat old target scopes will fit those block. Centerfire blocks dont have the eyebrow cut, they have a half cylinder type cut the screws in the rings lock into, to prevent recoil from moving the scope on the blocks.
Hope this helps,