I've seen some Schwinns like you mentioned. The filler is probably not
lead, but a low temp. solder of some sort. The one I worked on the
material acted more like aluminium than lead. Probably some sort of
La Mesa, CA
Mssrs Schmidt and Hollenberg have, I hope, come to agreement that some
Lasers do and some don't, which is good enough for me.
For your reading pleasure, a Real Story. It was a long time ago, and
was using a little propane torch for stripping the paint from our
1950s Schwinn Town & Country tandem, a fine, 4130 chrome-moly,
fillet-brazed beast. Suddenly, there was a splatter. Then more. Yes,
those long ago days of yore, before OSHA*, Schwinn used a bit of lead
smooth the joints... I can't remember what I replaced it with, but it
was probably bondo. :-) FWIW, a lot of lead was used for custom auto
bodies in the pre-Bondo era.
*Caution: If you think OSHA is a town in
Wisconsin, you could get in big trouble.