The additional photos make it clear that 'spectrum' has a Weaver top-mount base, (with pivot-rings), that has been improvised into a side-mount.

I wonder if the original 'user' aimed with his Left Eye, while shooting Right-Handed?

The off-set is much greater with this rig, than with the Weaver Side-Mounts, made for U.S. Krag receivers.

'Spectrum' is correct about the Ocular Lens Housing, of a regular side-mounted scope, interfering with operation of an unaltered Krag safety-lever. The cut-off lever, however, is not obstructed.

(IMHO - A Weaver No. 2 side-mount base will fit his hole spacing).

It is nteresting how the scope is rotated 90 degrees so that elevation knob becomes windage and windage knob becomes elevation.