Just found the answer. For those interested the answer lies not in the machine but in the Lens system. Confusion
This is from Russ on his SarbarMultimedia YouTube channel:
The difference is small and all to do with the lens tube diameter. The C series is 24mm diameter and is fixed to the head with a collet type clampring. The E series is 25mm diameter and is fixed to the head with split sleeve clamp and thumb screw.