Argo44:

As far as what I have read, those choke marks & steel types are not proof facility stamps but rather advertising applied by a maker. I for one think that since proof wasn't obligatory that the mechanics wanted to assure the end user that they were purchasing & using a quality product? But then again, I do wonder which end user read the adverts & actually could decipher & understand the mechanic applied touchmarks. But I believe you do have a valid question: what type mechanic applied the advertising and when? I would say the mechanic was a tube guy. And a follow up, where are the stamps residing today?

Cheers,

Raimey
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