It may have been a request for a different length barrel which an S&W letter will verify. Or more likely to replace a barrel with a bad bore. Isn't it nice that Smith stamped the new barrel with the matching serial #?
The tip off to a barrel change for me was the ejector knob which is the post c. 1930 style. Your revolver originally came with the 'mushroom' style that required a different notch in the barrel; neither of which were available in 1944. Shown here on 22/32 I frame Target (top gun):
Your barrel and ejector style:
