please give the weight of the rifle and the barrel diameter at the muzzle when you have it in your hands. this Geco rifle is not realy rare, you find it in 10,75x57 and 9,3x57 maybe also in 9x57 mauser and other. if we have a period Geco catalog it could possible get a name.

a drilled and tapped action is a special surprise sometimes. I got this when my Husqvarna was coming from denmark and there was nothing about it in the description before.
a gunmaker could hide it so good as possible be filling the hole's restore the engraving and blue it.
my own solution was a claw mount with a old Oigee 4x scope.

my rifle before

and after it got a claw mount