Bulova 1954 Clipper

Apparently not all of the Clippers used this movement. But since posting this I've seen it in another 1955 Bulova "Clipper" and a parts movement with the Clipper dial and a date code of "L8". So Bulova used it for at least these 3 years in Clipper models along with the 10CSC movements. In the models that had the 9ARC movements, Bulova used a spacer ring (Bulova part # MR313). Also found that the balance assembly used in the 9ARC movements is interchangeable with Bulova 9AR-8BBA-10CSC movements. Wonder why they used two different movements in the same model watch.