This is a subject that could easily fill many pages. The bottom line is that *IF* you are discussing what was used on some lehigh area rifles, primarily 19th century, you will need a sealer to prevent the wood from taking up finish coats and imho this was likely shellac or seedlac. I am only talking about a sealer, to fill the wood pores and render it largely impermeable to the overlying colored 'violin finish' that will be the actual finish itself. Most of these (again imho) do not look to have been stained - that was the point of a quicky sealing coat and a colored finish: To avoid hitting the stock with anything water based and to come up with a very colorful, attractive finish that is fast drying and can be applied quickly.