OK. So I am very happy with a new pair of 1000ft mitchell film magazines and here is one sitting on top of the animation camera. However, these mags have a wider base fitting known as NC (newsreel camera) and the camera uses one called GC which is smaller. Just waiting to hear from someone in LA who has an adapter. Hopefully not to expensive.

These mags are for the eventuality when large runs of film need to be exposed, possibly towards final prints for exhibition. Magazines can also house exposed film for certain operations such as long runs of rotoscope material, or at least longer runs than what 400ft reels can afford.