Brother Drew added some good places to look, but in the first one, I believe that is for the higher graded guns. They were a hand applied finish and used as many coats as it took to fill the pores and to bring the beauty of the wood out.
The factory finishes on the lower grades from post 1913 Specialty Grade, Ideal and Field Grade were either shellac or varnish. As for a stain, it is described there also.

David