Well, 9 out of 10 work fine, can't really complain.
Aren't they simple! Just the actual II, an objective lens, suitable PSU amd that it it. The prisms are redundant if putting in front of a camera, also reduce the weight by 50%. The objective lens also contains the mechanical iris so that needs to be used as well.
Only found a couple of useful web sites, anyone else have a data sheet please?