Hard to say James. It could be I suppose, but Stevens was usually pretty good about making sure everything matched. Even non-Stevens Win. or Ballard rifles that were worked on by Stevens were meticulously serial numbered so barrels would match numbers with existing receivers. They even marked the barrels as rebarreld, or rebored by Stevens.
Sounds like the trigger group may have been changed or barrel changed, but I'd bet it was always a DST gun, as regular 44 Stevens didn't have removable lower tangs, like the set trigger guns did. The 44 1/2 all had removable lower tangs though. That low serial number on the tang sounds typical of a 6 o'clock extractor.
I don't have any info on what Stevens might have done if they converted a regular 44 to a 45, or how it might have been marked.