[johngross]

I came across a 6 cavity brass conical bullet mold with Colt markings

In Robin Rapley's book on Colt Accoutrements, he pictures and discusses the Armory (Gang) Mold for the Walker. He states the mold is blued steel and makes no mention of Colt markings, just stamped "US". I take it you have a different source for your information?

John Gross