They look to be walnut. The holes are from a steel or brass plate that a few LEO's would put on the bottom.

Don't use filler. Find some walnut and make small plugs that you can force into the holes with a touch of wood glue and sand. You want to try to match the grain, which should be easy. Make sure to cut the wood so the ends of the grain show as you look at the bottom of the stocks.

The cut-out is also modified, that would be a tougher repair. With a little time, you could find a better set for little more $ in the classifieds here.