As has been said, your pawpaw's gun is a Model 58 which is an uncommon and somewhat desirable gun. A bit of history on the M58 if you're interested:
The .41 Magnum was conceived by several individuals who felt that, at the time, the factory loadings of then-available revolver cartridges were less than ideal for police use (revolvers were, at the time, the nearly universal choice of U.S. LE agencies). Notable among these individuals were gun writers Bill Jordan, Elmer Kieth, and Skeeter Skelton. As originally envisioned, the .41 Magnum was to be a dual-purpose police and hunting cartridge with different guns and ammunition tailored to those specific purposes.
On the hunting side of the equation was the S&W Model 57 which was available with barrel lengths of 4, 6 1/2, and 8 3/8" with fully adjustable target sights large target stocks as standard. As far as hunting ammo, Remington offered a 210 gr JSP at 1300+ fps.
Conversely, the defensive gun was the S&W Model 58 which was offered with a 4" barrel only, fixed sights, and smaller "Magna" stocks. The "police" loading intended for this revolver consisted of a 210 gr LSWC (this was before the popularity of JHP bullets) at a bit over 900 fps.
Unfortunately, the .41 Magnum never really caught on as a police cartridge and both the "police" ammunition and the M58 were eventually discontinued. There are several theories as to why the .41 never achieved popularity in the police market and all of them probably have a bit to do with it. For one thing, the Model 58 is a fairly large and heavy gun and, as such, many cops didn't want to give up their lighter, easier packing .38's and .357 Magnums. Similarly, some people inevitably wound up with the "hunting" ammo in the "police" gun and most found the recoil too severe for defensive use. Finally, both the "hunting" and "police" guns and ammo were marked with the word "Magnum" which, at the time, was not politically correct for a cop's gun. Perhaps if the "police" ammunition had been loaded in shorter cases and marked ".41 Special" more departments would have considered it.
Personally, I've always found the Model 58 to be a fascinating gun and have pined after one for years. Much like the Model 13 .357 Magnum, there is something inherently interesting to me about a revolver which looks like a run-of-the-mill .38 Special but delivers magnum power, sort of a "wolf in sheep's clothing" persona if you will. I also think that with a moderate loading like Winchester's 175 gr Silvertip that it would make a superb defensive gun for those who don't mind the size and weight. Finally, the older I get, the more and more the ruggedness and "all business" look of a fixed-sighted revolver appeals to me.
My "happy tax return" gift to myself this year was the "sporting" counterpart to your pawpaw's gun in the form of a Model 57 with an 8 3/8" barrel. While I've not shot it as much as I would have liked (my regular range just reopened today having been closed since early January
), I am quickly forming the opinion that both the gun and cartridge are vastly under-appreciated.
