I'd say Tange, but maybe not a Kuwi...
chain stay are tange like - same as an areo pro burner, but you don't have the seat tube flare like an Aero Pro
I have a Tange Rhino Charge I picked up a few years ago that is very like this (mine has the seat tube flare at the bottom that this doesn't)
if it's a US frame, I'd say Cycle Pro??
- I know Tange supplied frames for them... still a good frame if not a Kuwi