Greetings Jerry: I hope all is well with you. The Gem D's seem to range roughly from #315000 to #357000. Confusion arises with the fact that Gem C's range roughly from #295000 to #350000 because these machines continued to be made for ICS while the D's were being made. Toward the end, the rare Model E's also were made alongside of the D's and ended roughly around #357000. I estimate there were less than 1000 E's made since the serials seem to start above #356000 and end before #357000. I don't know of any records with serials at the Edison site so I put this out to this learned list, are there any serial number records at the Edison site? Given the simultaneous assembly of both black and maroon Gems, it is entirely possible that black Gems were on occasion repainted for a maroon Gem. There is likely no delineating time line for this practice. May all your finds be rare ones. Best wishes, Al Sefl