If some of the pictures of the 150 are really of a 150, then it isn't a 150. In the "27" picture (sorry it is a bit dark), there is a spot near the rear of the scope where the wood is cut down and there are two screw holes in the barrel. I believe these to be for an original scope mount that was made for the gun.
This post contains pictures of a military 65. It has no front or rear sight, but has a scope mounted using the two holes I speak of. Makes me think it might be a civilian version, maybe a later version when they started using sights, but didn't bother to remake the barrel or stock configuration...?