I had a flaking Baker that I stripped to bare wood using only rubbing alcohol, so it apparently was finished in shellac. Similarly, I've dissolved added shellac off the top of the remaining varnish or lacquer original finish of other guns. This is the reason I start any stock cleaning with Murphy's Oil Soap and then proceed to Ammonia before resorting to mineral spirits or alcohol, and onward to hotter solvents. Sometimes, I find what I'm looking for under a layer of grime without resorting to a total strip and refinish.
Since I've had various original stock finishes dissolve in various solvents, I think it's safe to say that gun makers then, as now, used different finishes.
