You've posed an interesting puzzle, Deano - -
If you're sure about there being five chambers in the cylinder, then we're ALL guilty of having jumped to an erroneous conclusion. That being the case, the revolver is NOT a Smith & Wesson Military & Police, nor is it a Model 1905.
About the only older-vintage, five shot, non-snubnose, swingout cylinder, double action, .38 caliber S&W revolver of which I'm aware is the .38 Regulation Police. This was produced on the old I-frame, noticibly smaller than the M&P, which was and is on the K-frame.
You write - -
I searched all over and all I can come up with is a four digit number on the inside of the butt that is 1177 . . . .
Again, we (I) may have misread what you wrote. If so, the problem is with my misperception, not your writing. You said right up front that you are not well versed in firearms terminology. Anyhow - - by "inside the butt" -- might you mean, on the front of the frame, inside the curve formed by the frame and the trigger guard? Reason I ask is that on this model, "The serial number is found on the front tang or forestrap." (From
Standard Catalog of Smith & Wesson, 2nd edition, by Jim Supica and Richard Nahas, p. 108.) According to the same source, the prewar .38 RP serial number range is 1 to 54474 manufactured between 1917 and 1940, which would certainly include your number 1177.
Problem is, the .38 Regulation Police model was produced ONLY in caliber .38 S&W, a very different cartridge from the .38 Special, though they are visually similar but for the length. There are various possibilities here.
--One, the revolver is indeed chambered for .38 S&W. Oftimes, we see what we expect to see, especially if outside our area of expertise. Could it be that the ammunition you saw with this revolver was headstamped, ".38 S&W" rather than ".38 Special?" Another possibility is that your Granda' might have either been unable to easily locate the S&W ammo after the war, or might have wanted to display the revolver and accessories, without the possibility of someone loading it.
--Two, someone ran a .38 Special reamer into the chambers, so it would accept the longer cartridge. This was fairly common with some larger-frame S&Ws produced for the British and then repatriated to the USA as surplus. While this may be acceptable with a K-frame revolver, it is a chancy proposition with the smaller, lighter I-frame, and I, for one, would be hesitant to fire it with .38 Spl ammo. This would be easily determined if you take a (verified) .38 SPECIAL cartridge and drop it into the chamber. If it goes fully into the chamber, with the rim resting against the rear cylinder surface, then it DOES take the longer round. An aside: The cylinder of a normal I-frame revolver is not long enough to accept standard length .38 Special cartridges. One would need to trim a bit off the bullet nose to make 'em function, or else use short-seated "wadcutter" target ammunition.
Couple of suggestions. As long as you're taking photos of the revolver, please bu sure to photograph the rear face of the cylinder. Also - - If this is indeed a I-frame Regulation Police model, the holster will be of interest - - Please photograph it from the outside, with the flap closed, with the flap open, and also from the rear, with special attention to the markings.
Also - - The various markings on the revolver are of interest. In which are of the military did your grandfather serve? Do you know where he was stationed, at any time? (Prewar, in wartime, or postwar.) I'm thinking of all the US made firearms I've seen with British proof marks on them. Also - - For citizens of certain countries, it might have been easier to own a firearm produced in Europe, and thus the "Made in France" markings . . . .
You present us with a topic of lively conversation, sir. I eagerly await your photographs and additional information.
Best,
Johnny