Not to "roach the buzz" of the stag OP, but in all my reserach fo old Colts, I saw wood, hard rubber, ivory, and -- most often as an exotic material -- MOP, but I never saw stag on an SAA until the 50s Westerns dreamed it up. Am I misremembering...? It seems logical, being a plentiful, cheap, and legal material, but it appears to have been rarely done pre-20th century. I could be wrong.
Stag looks great on 1911s and S&W N frames though...