Maybe a Diamond lamp

Larry,

That is a distinct possibility. However, one thing I'd like to mention is, I think the insertion of the baseplate was the really technical part of creating a fount. I suspect specialised rolling machines would have been needed. I suspect there would have been specialised soldering machines similar to patents I have found for soldering lids onto tin cans. There may have been a combined rolling and soldering machine.

I had a lamp, a lamp that is now with another collector, which had a fount that looked exactly the same as one that National Stamping (Nulite) used. However, after carefully measuring a known Nulite tank then the lamp tank that I once owned, it was clear that the bung hole was about 10mm closer to the edge of the fount. It was a small but tangible difference.

I think many of the early GPA companies, that were doing hollow wire, eventually manufactured their own tanks. Those hollow wire tanks do not offer the technical challenges that portable lamp tanks do/did.