Mr. Gumm sent me a text message regarding this.
I've sent him back two responses explaining the possibilities of what is going on.
1. Mismarked gun
2. Worker "lunchbox" gun
3. Post manufacture gunsmith conversion.
I highly suspect either No. 2 or No. 3 given the simple fact that factory records show ONLY one flavor of Model 58 during its original production run -- .41 magnum, 4" barrel, fixed sights.
A 7 3/8" barrel is NOT a factory length barrel, but it could be a simple mismeasurement and would relate to the 8 3/8" barrel that has been a factory staple for nearly 100 years.
He offered, and I've requested, clear photographs of the guns, the markings (including inside the crane cut).
As I said in my previous response, I've heard rumors of Model 58s having been factory made in .44 Magnum, but as far as I can tell, no one has ever actually seen a factory authenticated .44 Magnum 58, there are no official company records indicating that any were ever made, and none of the major S&W collectors I know of have ever claimed to have proof of one existing.
Some of us, I think, have heard the same thing about the Model 28 -- S&W made .44 Magnum AND .45 Long Colt Model 28s!!!
Uhm... No, they didn't. People like Hamilton Bowen have, but Smith & Wesson didn't.
So, as I told our enthusiastic Mr. Gumm, I'm not at all ready to say "OOPS! I was wrong!" without a lot more information.
And at this point, I'm going to maintain that I am correct.