As hinted by others, unless a special order gun, most of the old gun companies used varnish, due to speed of application alone. Oil finishes took days and weeks.
I am gonna throw out something likely controversial, but more than one stock guy agrees, where their specialty are old guns. It goes back to what the goal of the work is. Too make it look just like it came from the factory? And in that case, most guys spend way way way too much time filling the grain, cause once again, even on guns like 21 Wins the grain rarely got filled except on perhaps the presentation class guns. Oil got used of course, especially in Europe, but the popular models and grades of American guns, were typically varnish.
Another thing is, an old gun the finish has shrunk from age, and often has open grain showing.
Every one has seen the early Wins with flaking finish. Thats cause they used a beeswax mix as a filler. I have no idea how they got it too stick this long either, but the wax filler is well documented.
If they are trying to produce a nice, but vintage looking gun, bluers have been known to take brown paper sack pieces, and knock off the blue on the high spots, to imitate some age.
Its often a bit like early factory engraving. If the engraving is perfect, its rarely factory. Those old boys worked on piece work. Duck often came out looking like chickens, and dogs may have looked closer to a coyote. Sheep often looked like some exotic pen raised critter.
Again, I am talking about the lower grades of factory patterns. Any that dont believe me, simply study some authentic early engraving some time.
But when a 100 year old gun is "too perfect" its like seeing a bent corner on a deck of cards used in a "friendly game" of stud. Someone in the game aint playing it straight.
A perfect finish on such a gun, is usually the first giveaway that its been redone in some aspect.
Whether or not the seller advises the buyer, is the key. And some have been known to forget.:biggrin: