Nice one Sam, if you can do a better shot of the bolt lowerflat it would be helpful, we have very few G88 with original bolts and to get the pattern clearly is important. This acceptance seems to vary a little, at least from the few so far recorded. Also the acceptance of the barrel, on this laptop I can't make them out clearly, maybe they will be larger on my main pc. I don't assume there is any sign of a blank supplier or potential trademark? It seems in most cases the original barrel lacks any supplier, but on re-barrels sometimes it is identified.
I added the report to the thread and will add to it or correct the observation as opportunity allows. Next to finding bands or SR with a unit marking (serial match) the discovery of bolt patterns are most desired! I think that even with the meager amount of bolt data collected good guesses can be made of loose bolts manufacture, - in some cases, Loewe especially, this is certainly the case, but the trends are already revealing little tidbits of probabilities that "eventually" become facts (probable facts anyway)