Josh,
On that pattern, I wouldn't get too hung up on the type of dubbing. It looks like a fly that is meant to get down deep fast. It looks like beside the bead it has lead wire ( or since it's Orvis, probably leadfree wire) underneath the dubbing. I am guessing that because of the profile (and because that's what makes these nymphs successful).
If you really want to know what's going on, buy one and dissect it with a razor blade. but I would use
Caddis hook
black thread,
tungsten bead
black thread
pearl crystal flash (ribbing)
pale dubbing (Hare's ear) for the abdomen
black dubbing with some flash in it for the collar
I have no knowledge of what Orvis uses, but there really isn't anything magical about this pattern. It is just a bead head nymph with a light abdomen, dark collar and Krystal Flash rib. The stock photo looks a bit chunky which makes me think it has extra weight underneath the dubbing.