I've got some of both Badger & Opossum, and depending on what's being compared, it's hard to tell them apart. I'm sure it's not Marten. Marten, Sable, Mink, Otter & Muskrat all have similar fur. What's posted, the underfur doesn't look to be any of those, not dense enough.
Back when I was tying commercially I bought a couple of big bags of Badger scraps, and used the hair for tying many different flies, particularly Bonefish flies. If the dark guard hairs & finer underfur is removed, Badger looks very much like a fine calftail hair. Some of the Badger I had, the guard hairs had some black/white barring to them, while some pieces were just dark. You may see Badger referred to as "Silver Tipped Badger" because of the barring.
I liked it better than calftail, because what I had was a bit longer & lacked the twisted hairs that some calftails have. Also, being a finer textured hair generally, the flies had a better action to them. It didn't hurt that for what I paid for the Badger scraps it was cheaper than buying the calftails too!
Opossum is similar, and depending on the animal, much of the hair will have black tips. It's another hair that works well for smaller flies, and those black tips can make a nice looking & sometimes very productive fly. (Tip dyed materials seems to be the rage now, but Opossum is naturally that way!) Opossum is also very fine textured, so again has some wonderful movement to it.
Both Badger & Opossum are very easy to dye!