they may have changed the motor assembly part way through production. so if you bought the jukebox from an operator, the entire page assy may have been swapped at some point causing the mismatch in part numbers you are seeing. the rowe 100a and the 100b are very similar in appearance, but often have different parts (while the main assy's are interchangeable, some of the components that make them up are different and not interchangeable.)