edit 10/16/12: of course, now that I'm in "upgrade mode" I'm researching like crazy.. and there seems to be a difference in models of the One S-
Another way to identify it is to start the phone in HBOOT mode (Press and hold volume down, and then press and hold Power, releasing Power when the back/home soft keys flash).
The HBOOT screen should show VILLE or VILLEC2 at the top. VILLE is S4, VILLEC2 is S3.
so I'm gonna havta to go either Best Buy of the TMo kiosk, or the TMo store in NH, and actually test for the processor before I agree to take it home. that ruins my plan to get it cheaper over the phone with CS.