Remington-Rand 1911A1s were shipped with magazines marked "G" on the toe. G for the manufacturer, General Shaver.
The holster and spare magazines add to that, but I have no idea how much.
The information about the original mag marking is handy it would be, I think, quite rare to find both together today, and even if they were, there is no certainty that the "correct" magazine is actually the original magazine.
Unlike some European nations (most notably Germany) our holster, magazines and parts were not numbered to match the guns. Which bring up a point about "original" and "in service". Collectors generally prize a completely original, and if possible unissued gun. They want all the original stuff it came with including the box. They RARELY get that, and that's why those guns are worth so much.
Once the gun gets to an "owner" unit, there is no attempt to keep the accessories (and that includes magazines) with a specific gun. A magazine goes in the gun, spares go in the bin. And same with parts, generally. "Parts is parts" has always been the treatment, if not the admitted to intent.
To the OP, can you give us any more details about your Grandfather's service beyond Army and Korea? What kind of unit he was in? what he did? anything like that, the more detailed the better. All the information you can gather should be written down and saved before it disappears forever.
The gun was manufactured during WWII, and it might have been issued to some unit then, or any time later. it might have been in Depot storage until Korea, or it might have been in the arms room of a unit.
I worked Army arms rooms and as a Small Arms Repairman during the 70s when identical pistols were still first line issue. I know how they were handled, stored, inspected and repaired in service at the time, and have every confidence that things were not significantly different in earlier years.
Not every gun wound up detail stripped in a vat of cleaner with a dozen others but it did happen. And when those guns got reassembled no care was taken about which parts came from where and what frame they got put back on. Other guns lived different lives, and always kept their original parts, unless some of those parts failed or were damaged, then the gun repaired.
I saw 3 actual 1911s (not A1s) in service. One was 100% correct including the grips and had only very slight holster wear. Another was nearly the same but with the WWII era plastic grips, and the 3rd had WWII grips and a couple of A1 parts.
SO, there is no "original" holster and unless you find an unissued still in the box 1911A1 you won't find it with "original" magazines only possibly period correct ones.
Which means you can get all the gear "period correct" as used in service but there is nothing to link the gear to any individual gun.
And, almost any combination of gear and parts from any makers is correct for "as used in service". Not the same as "original" meaning as delivered to the military from the maker, but fully authentic and correct for "as used in service".
As a guess, but a fair one, I think, the pistol in the OP was issued your Grandfather, with what ever holster and mags that were grabbed by the supply clerk, came home with him and saw very little use since. Not an uncommon thing.
The proper GI holster and mags do add some value, as items but do not add a large "historical premium" in $.
With a Luger or a P.38 which have numbered magazines the correct matching mags adds considerably to the value, same with the other numbered parts. It makes them worth more than guns with mismatched numbers.
This is not the case with 1911A1s.
Shooting the gun a little won't hurt it. Turning it into a competition gun or an EDC carry piece with all the "bells and whistles" aftermarket parts, etc., would be a travesty, in my eyes. Doesn't sound like that is the plan, which is a good thing, I think.
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