Vilhelm, welcome to the Heavy Duty fan club! I agree that with that serial number you are probably looking at another July 1946 gun. But we cannot be completely sure because S&W did not follow a policy of shipping in serial number order. Records show that HDs in the S62xxx through S68xxx range were shipped in July, but other guns in that range were known to have shipped in 1947 and even 1948. Only a letter will answer that question.
N-frame .38s are fascinating revolvers. If you think of them as .38s, they seem laughably huge. When you shoot them, even the hottest .38 special loads seem as tame as .32 Longs in a smaller gun. The fixed sight guns are very accurate. For the ultimate .38 Special range trip, get your hands on a .38/44 Outdoorsman -- same frame, but with target sights and a 6.5 inch barrel.