the initial design as supplied by Campagnolo when the braze on front mechanism was introduced was stamped. Soon enough there were investment cast versions that extended the attachment surface farther around the tube's circumference. A Superior design. When Those were in reasonably wide distribution, Campagnolo dropped supplying the stamped mount with the derailleur.

should note that Shimano supplied an investment cast attachment part with the EX era AX front mech. it was an orphan and not compatible with the Campagnolo scheme.