Yeah, it looks like it.
I thought perhaps a recoil crossbar/key might fit in that space...somehow.
I seem to remember dovetail receivers on centerfire Brnos, CZs, and Sako's. Sako dovetails are tapered wider at the forend so the rings can't move forward under recoil and the Brno and CZ use some recoil stop.
Generally though, dovetail mounts/receivers I have come across more with rimfires than centerfires.
Also rimfire dovetail integral grooves are spaced 9mm - 11mm apart and don't need recoil pins due to the .22 low recoil. But these rings I have seem to be made to fit 19mm dovetails which would be for centerfire rifles mostly.
I doubt it is common to see centerfire dovetail rings with no recoil pin or crossbar like these ones... as without them, the scope will move forward under recoil. That's why I seem to agree with @NewbieZAR that perhaps it is missing a piece.
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