Yep, game-changer. The embossing was done with a large stamp, which I doubt can even be manufactured today. They likely did come from Baldwin. You may indeed have quite a collection there.
I don't know about print-making in the 1870s/1880s, but these may have been printed from the original negatives. An expert would need to examine the paper. The cropping makes me think they're copies. Original builder's photos will not cut off the pilot or tender at all, and would be on heavier stock. They are all builder's photos, because the backgrounds have all been taken out.
David Fletcher, an expert on engines of the period, may be able to help. I can try to get his contact information if you like.
