$12.50 indeed. I missed that bargain. The best I ever did was $20 and it was a bakelite Baron. Yours as sold has nice looking numbers. The seconds wheel always looks the worst and usually does not turn very well.
I also do not understand changing out the rotor shaft. The cyclometers use a B2 rotor with a threaded stubby shaft.
The number wheels were very dirty, so I cleaned them slowly and carefully, trying to remove the dirt and leave the numbers.
The replacement rotor originally had a different type of output shaft. I had pulled it apart a while back because it was noisy. I gave it a cleaning, new oil, and the shaft from the other rotor.
Larry