I have marine air horns from Kahlenberg and Cunningham, and both use
all bronze bolts and cap screws that have the infinity figure-8 symbol
on the heads. Does anyone know the manufacturer of these? I've seen
these bolts on horns from 1951 through the mid 1990's, but I can't find
the supplier.

Thanks,

Adam

These are silicon bronze fasteners. Availilable from Mcmaster Carr
Supply.

Good luck.

Tom Lipton