LUX FN49 stock question

I recently came into possession of an AL contract 49, all matching (but no matched bayonet:() and appears to be all original. What is odd is that where the later rifle would have a cross bolt, mine has wooden plugs inlaid. Serial # is in the mid-5k range. I am guessing that it is some sort of transitional model between the non-bolted early rifles and the later bolted models. Wood appears to be light European walnut, and the plugs are darker. No import marks found. Any thoughts?