Actually there was a concerted effort to pull and replace the crucial fixed pitons in the Gunks quite a while ago while leaving some of the original relics in place. The tipped and sometimes shallow nature of the cracks created a lot of perfectly disguised timebombs as the resident moisture rotted out the pitons quickly leaving little evidence to visual inspection.
Flow Ree- Congratulations on the ongoing success of the family concern!
Has anyone at Sporthaus Schuster archived the catalogs and hardware that you sold along the way?
I don't have any Sporthaus Schuster catalogues from the 1940s, so I am not able to reason any better than you are now doing yourself.
Sporthaus Schuster started as an international trademark in 1926, but that does not necessarily mean that they put an ASMU sign on their pitons in 1926. It's quite possible that they sold un-ASMU-marked pitons the first few years.