Checking the database, I find a run of 5" guns leading into the S907xxx range. At about S9075xx, there is a switch to 6" barrels that lasts nearly to the end of the S909xxx range.
The earliest ship date in this group is April, 1947, and the latest is July, 1947. What is interesting is that the April shipment was of a gun that went over to King for the King Super Target modification. It had a 6" barrel, as one would expect.
Another interesting feature of Redcoat3340's revolver is the extractor rod knob. By this time, the knurled end had largely superseded the knob. However, between S903000 and S908000 I have located three revolvers that still had the knob on the extractor rod.
All three have 6" barrels. All the other 6" guns in this range that have shown up had the knurled end with no notch machined into the bottom of the barrel. This might reflect the paucity of 6" guns being produced in 1946-47, with a few older 6" barrels already notched just sitting in the bin.
It is fun to speculate on matters like this!
Edit: It turns out that the gun which is the subject of this thread was already in my database. So, correct what I posted above. I have only located TWO (not three) 6" guns in this serial range that have the knob on the extractor rod.