Yes, the clip is removeable with a torx key I forget what size. The knife is made in China by a maker called SanRenMu, and it corresponds to SRM's 723, but with Buck's cosmetics. SRM also makes a smaller version, and Buck offers that as the Colleague, I think the name is.
I'm not 150% certain that SRM is the maker. But SRM's design was on the market first, then Buck's Chinese-made version appeared a year or so later. Guessing that SRM makes Buck's Nobleman doesn't seem like a stretch to me.
As regards any important differences in materials and manufacturing, I can't say. The SRM 723 is a nice knife, frame-locking, and opens easily and I'd expect the Buck version to do the same. I took the clip off my 723, so I can't tell you much about how it handles using a clip.