The answer to your question is a fairly obscure detail in a fairly obscure “niche” of knife trivia. The lack of response is probably because no one that has seen your question has an answer. I’ve been collecting Case knives over 50 years and I don’t have a clue.
Plus, if someone can answer from just looking at the end view of the bolster, I’m gonna be really impressed. When your post said “muskrat blade” I’m expecting to see a picture showing the blades, not just the butt end of the knife. So if your question can be answered from just looking at that view of the knife, again, I’m amazed.
Doesn’t bother me to admit, I have no idea.
If you do find an answer and it’s not from here please come back and enlighten me too!