Not to be a grammarian here, but "PROFESIONAL" is not a mispelling at all and it's not a "Mexican spelling" either. Mexican is not a language. However, Spanish is a language, and in Spanish, the English word "Professional" translates to "Profesional." There are no uses of the double "SS" in Spanish.
Anyhow, nice bike. I have the exact same frame (minus the nice NR parts and the perfect looking paint job) and same color. For what it's worth, I think that it may be a late 70s model rather than an early 70s job, due to the fact that it has brazed on shifter bosses.
Ken Bensinger
Brooklyn, NY