Dick Hosmer wrote on Sep 24^th, 2019 at 5:36am:

SA had to pay a royalty on every Krag assembled, so VERY careful records were kept as to how many were made.

I have wondered if spoiled receivers were replaced in the numbering sequence. You statement makes it clear that bad receivers would have had to have the number replaced or noted as scrap (leaving a void in the numbering sequence) to avoid paying the royalty.
Does anyone know which was done? Might explain the other receiver with the odd number, made from 2 sets of stamps.