Thanks for the clarification, Deeton. You said what I meant to say about the "Professional model" engraving. The owners manual of that era said the "Professional Model" designation corresponded to the Combat Selector sights, but as a practical matter that meant just the Mark IV and Mark VI, and this engraving was eventually discontinued. So, as you stated, the "Professional Model" engraving will be found only on the Mark IV and Mark VI models that were made around the time the stainless guns numbered 10000 and above began to be made. I don't know what the last "Professional Model" engraved gun was numbered.

Forgot about 10000. A rare gun indeed.