From my rifles and those on the net the mounts and scopes were retrofitted. The side mounts are not uniform. These mounts appear to be a variety of common side mounts. Neither of mine have a maker or retailers name. These mounts are attached to the rifle with three slotted screws. There is a small piece of wood removed from the top edge of the stock to make room for the base.

On the 146, the scope base is left in place. The scope and ring portion are gone. I'd rather look at that base than three screw holes. The 146 stock appears well bedded with no cracks. That gun is ready to go. Husqvarna rules. I have no way of knowing but there may have been jigs and fixtures to locate screw holes and stock modifications.