Mike,
Did the commercial Heym action have the thumb slot? What does the boltstop look like, is it a military type or the FN type? I was in their office in 1971 and there were examples of rifles they made before that, but I didn't have a chance to examine them. They were making the 2000 series, etc, then but I don't know when they started. On my second tour, the Heym family (Frau Heym) had won a court case and recovered full ownership of the company, so they didn't make them anymore.
Mikew