Hi Richard
As with many CMP parts there are variations, and differences in how they were made. I suspect that a lot of these small assemblies were given to small subcontractors and how they were made was best suited to what that contractor had equipment to do. They may even have been slightly modified to make use of left over steel stock trimmed from larger parts.
The result is your box and the one on my `45 HUP are slightly different in dimensions and method of assembly mine box is all formed from a single piece of steel. The computer just turned up my CAD drawing for the mine, Ok got a file format I can post to MLU.
Will photo graph my boxes tomorrow.
You got to love MLU somebody needs info and within hours others are helping provide an answer.
Cheers Phil