A picture of the seat stay to seat tube connection would be really helpful. Many builders use that area to show their distinction from others. Also a shot of the entire frame would also be really usefull. Like Unworthy, I'm really baffled by some of the unique features of this frame. I don't think the braze-ons on the seat stay are rack supports. The ends are scalped so that is not the shape that would support a rack strut. They have a small hole and like the same one under the BB, they look like a guide for either a cable or a wire. I just an't figure out what cable or wire.

The possibility that this frame was made by a hobby builder seems solid. The C being a bit off center on the lug is a bit amateurish. However the clean shorelines indicate a builder with decent torch abilities. It might be a collaboration between an experienced American builder with an inexperienced customer wanting to be part of the process. That might be why there are no decals.