Anyone know where CB350's in the 1970's were manufactured?

I'm trying to track down which factory produced the cb350's in the 70's. This page has some good info, but it's focused on the 4 cylinders (http://www.sohc4.net/honda-factories/).

Not much info on the smaller CB's and their manufacturing sites. My guess would be the Hamamatsu factory. It would show a letter "M" on the VIN tag but I don't see letter designations in the VIN's.