Howdy
A little late checking in on this one, so I will try to answer as many questions as I can.
The 38 is a 38 Military and Police Postwar Model. I cannot make out the serial number very well, but as suggested the serial numbers for these ran from S811338 in 1945 through S99999 in 1945.
There really is no such thing as a Pre-Model 10. The 38 Military and Police model was manufactured from 1899 until 1957, with various iterations. In 1957 Smith and Wesson went to a model numbering system and at that time the 38 Military and Police became the Model 10.
It is difficult to tell from the photos, but yours looks in perfect condition, I doubt very much it has been refinished. Run your finger tips over the markings stamped on the barrel. If you can feel slightly raised steel around the letters it has not been refinished. When refinishing a revolver, the polishing process usually wipes away the slightly raised steel around the markings. The grips look correct, for that model, and as noted one of them will probably have the serial number of the revolver either stamped or written in pencil on the underside. The serial number should show up in four different places. The number at the bottom of the butt is the serial number of record. The number should also be stamped on the flat on the underside of the barrel, rear of the cylinder, and underside of the extractor star. That one is usually pretty hard to see. If the numbers in the other three places match the one on the butt, the gun shipped with those parts. It should have the current hammer block on the inside, which S&W began using after a shipboard accident in 1944. So it is completely safe to carry fully loaded with six rounds. The caliber marking on the barrel is 38 S&W SPECIAL CTG. CTG stands for cartridge. Smith and Wesson always marks 38 SMITH & WESSON SPECIAL instead of just 38 Special to let you know they invented the cartridge in 1899. The hammer is the old long throw or long action hammer, which would be correct for a Postwar M&P made around 1945. Still lots of Case Hardening colors on the hammer and trigger. Nice box, it is correct for about 1945 or 1946. Frankly, I would be tempted not to shoot that revolver, it is just too pretty. It is your gun, do with it as you will, but I would probably lock that one away in the safe along with the box. Nice that you got the instruction manual with it too.
About the Registered Magnum, that is the only gun left on my grail list that I have not gotten yet. The very first N frame 357 Magnums were the Registered Magnums, in 1935. As a promotional program, S&W registered the serial number of the revolver to the owner. S&W was overwhelmed with sales of the Registered Magnums after building about 5,500, and discontinued registering the revolvers to owners in 1938.
As you have already been told, that is not a Winchester barrel on the 32-20 Hand Ejector. 32 WINCHESTER CTG was just another name for 32-20. This one shipped in 1916, it is a 4th Change. If you can read it, the caliber marking on this one is 32 W.C.F CTG. 32 Winchester Center Fire is the alternative name for 32-20. Not really much bottle neck to the 32-20, it did not give much problem with the cases being shoved back out of the chambers, there was not enough of a bottle neck angle to cause the empties to wedge backwards out of the chambers. The one you are looking at is probably a little bit older than mine, with the round butt and hard rubber grips. I'll tell you, I would be all over that one for $700. I paid $800 for mine a bunch of years ago. Yes, Starline still makes 32-20 brass, but they are out of stock right now.
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Yes, that is the most recent edition of the Standard Catalog of Smith and Wesson; the 4th edition. Published in 2016. I prefer the 3rd edition, I am more used to it and it is easier for me to look stuff up in it.
Yes and no about the lockwork being the same with the new ones. A number of years ago S&W started using Metal Injection Molded (MIM) parts for the lockwork, as opposed to the old machined parts. MIM parts are less expensive to make than machining parts from solid steel. Also, the configuration of some of the parts has changed from the old machined parts. Volumes have been written about MIM parts vs machined parts, I ain't gonna start talking about it here.
Just to give you a taste, here are the parts inside a Model 17-3 made in 1975. Mostly machined from solid stock.
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Here are the parts inside a Model 617-8, made in 2003. Most of the parts are MIM parts.
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Incorrect. Rifle barrel groove diameter for 44-40 was originally right around .427, although it varied all over the place. Groove diameter for 44 Russian, 44 Special, and 44 Magnum is .429. When I load 44-40 I use bullets that are .428 in diameter. So if we are going to round out to 2 decimal places, all of the above are 43 caliber.