The sights are definitely aftermarket. I'm not sure what the wood piece would be for the rear sight unless it is a makeshift spacer of some sort. The hole under the butt trapdoor appear to be filled with epoxy, along with the butt stock ahead of the buttplate.
Do you know the last time this gun was shot? You may want a gunsmith check it out in case you plan on shooting it yourself, just to be on the safe side.