The Burt Co never hot stamped chips for anyone.
They shipped blanks to distributors.
Burt felt there was no security what so ever for hot stamps. They felt they could be copied by anyone, anytime.
The mold was sold by many distributors over the years. It was actually an "open" mold for much of the time.
Bud Meyers has a few PCC records with DiSq molds.