Yeah, I've heard about gas welding too, but it's difficult to translate technical articles both because they use lots of jargon and even worse, historical jargon. I've run across it in some older French articles. It's more just the idea popped into my head offhand because the mix between the tiny Routens brass fillets and the big non-brass fillets was so conspicuous. Also now that you mentioned the Schwinn, I remember reading that one little mention on Sheldon's site about them, so maybe it just subconsciously made me think of that.

I've also heard about the custom Herse BB shells before, but now that I think more about it, I rather like the idea of it. It seems a little more authentic than brassed "lugs" for silver, and any serious heat damage is kept to the lugs.