Being pressed for time, I didn't go back and look up your earlier post, and just presumed it was a .38-200.
It may or may not have been a DSC revolver. Pearl Harbor was bombed on December 7, 1941, and while I was young I still remember trying to wake up my father and tell him. Three weeks later it was 1942. Within those three weeks president Roosevelt had issued the order to put the previously organized DSC into action. Only Roy Jinks at Smith & Wesson can tell you if it shipped before the DSC took over or not. That information will cost you a reasonable $50. As a point of reference, the U.S. Navy bought 3000 .38 M&P commercial revolvers in .38 Special / 4" Barrels / with lanyard loop, around March-April-May, 1941 with serial numbers in the mid 740,000 to high 752,000 range. Concerning your revolver, keep in mind that there can be a vast difference as to when the frame was serial numbered and when the finished gun left the factory. This was especially true at this time of history.
As for the hammer. Long-action hammers designed to use the new hammer block were first used starting in January, 1945. An "S" was added before the "V" serial number prefix, and the first one was SV 769,000. Thereafter S&W continued to make new revised revolvers while retro-fitting older ones. All of the ones I have seen had the wide D.A. sear.
The first short-action hammers had the narrow sear, and were introduced with the new K-22 Masterpiece target revolvers that came out in December, 1946.
Short-action/narrow sear Military & Police .38's didn't come about until February 1948. Post-war, long-action M&P production (with the new hammer block) started in September 1945 and continued for a short time after the short-action was introduced. Post-war / long action .38 M&P revolvers have serial numbers that have an "S" prefix that started at S 811,120
I have never seen one, but it is possible that to complete some of the long-action .38's they made some long-action hammers to take the then current narrow sear. If so, Roy Jinks would know. Then at a later date, it is possible that someone replaced the original hammer in your gun and in its place installed a long-action/narrow sear one. I can't see any other way to explain it.