S&W44:
You scored bigger then you may have thought. Your Post-war .38/44 Heavy Duty has the pre-war "long action."
Smith & Wesson reintroduced the .38/44 Heavy Duty in 1946, which was identical for the most part to pre-war production, except for an improved hammer-block safety that had been used in K-frame revolvers since late 1944 or early 1945. To denote the addition of the safety a letter "S" was added as a prefix to the serial number which continued from the original pre-war series. New production started at S62940. At this point S&W retained the old-style "long action, which you have. A new "short action" (which is still used today in general form) was introduced in 1948. With only two years of limited production "long action" post-war .38/44 Heavy Duty revolvers are scarce if not rare - especially in the kind of condition your gun is in.