J.B. Patton,
Generally, Heym would use their own actions. Most any action can be "side plated", upon request of the customer(with appropriate price adjustment). This work was(is)usually "farmed out" to a local gunsmith, who often had a "daytime job" at the factory, or had previously worked there. My old German gunsmith friend often did this type work for Heym( post War). In fact, he did the sideplates on the Ruger #1, Heym built up for John Amber, and was reported on in Gun Digest. He also was able to convert existing guns( O/U and SxS) to sidelock, and from shotgun to combo gun or double rifle. Consequently, it is possible to find several different configurations of guns, all starting with the same basic action. The Engraving on such a special order gun would be "farmed out" to a well known outside engraver.
Mike
