John,
The theory I've always heard was that Pack purchased variant hilts for some of it's Pioneer & Feuerwehr models from other manufacturers which was one potential explanation for the lack of spanner nuts on some Pack products. I have 5 Pack fire bayonets, all with different maker marks (of course). Only 1 of the 5 has spanner nuts, the other 4 have centered rivets. Some of those have very obviously non-Pack hilts, these are likely Horster IMHO.
That said, I have several distributor marked fire bayonets that are not Pack marked but clearly Pack produced with Pack hilts & offset rivets. I would say, based on own experiences with Pack Feuerwehr models that there are a number of variant grip/rivet/hilt configurations & any number of potential explanations but it's clear (at least to me) that Pack did indeed produce some Pioneer/Feuerwehr models on it's own while also procuring hilts from other manufacturers.
