Not sure about the DT serial numbers, but a bunch of 3-gun sets were made by Turnbull for Sporting Products in Florida around 2007. These were the SP serial number ones. Originally, supposed to be limited to 50 sets, but not sure how many were actually made. The 3 gun set was made up of an A engraved with Walnut, B engraved with Stag, and C engraved with Ivory. These sets were broke up and sold individually, Cabelas had numerous ones a couple of years ago.
I have a copy of the ad for this series in the Holiday 2007 issue of the Dakota Arms magazine they put out for a few years.