Just to add to the pot, my 199A is a possible factory built bista bike. It has the old style tapered top yoke and the motor and frame numbers don't match but are only off by 4 digits.
I realize the top yoke could have been changed over the years, but I find it odd that the motor is some sort of dealer replacement being that close to the frame numbers and was more likely done at the factory. Maybe it was built on a Friday after lunch lol.