It's Dynamic! -[ HMM ]-

Model name cast into a one of a set of Neumade film rewinds (similar to the set pictured at this link, but taller and configured for larger-capacity 35mm reels).

 

X-3 sounds more like a code name for a 1950s-60s rocket or supersonic aircraft, not a model number for a piece of film equipment made of cast iron.

Done