I damaged the stock on my #1 a few years ago. Had one hell of a time trying to remove the factory finish. A call to the factory and a short conversation with the shop foreman answered my question which is the same as yours. Ruger uses a polyurethane finish on their walnut and hardwood stocks. Very tough to remove even using the proper strippers. A bit of patience and some wood finishing experience resulted in a flawless finish that catches everyone's eye where ever I show up with it.
