There is no such thing. The Krags were rebuilt at the armory and arsenals. Given the available information currently in existence, it would take an expert opinion of whether a gun was "as made." Even then it would simply be an opinion. Because there aren't enough records to determine exactly which parts were used and when. Making that worse, the parts aren't marked. German Mausers (K98k) have each part serialized. Krags don't have that (except the first 11K model 1892s which have it on 5 parts).
The armory rebuilt the guns. With frequency.
Yes, I can review a Krag and make a very education opinion on whether the guns is "about right." I wouldn't guarantee it though.
There are two different "conditions" which affect value:
1) As made. Almost impossible to assure this.
2) As issued.
#2 would be whether the gun only exhibits parts which would be expected from an arsenal. No after-market modifications.
Krags are rated against #2. Due to the issues with #1.
The first 11K model 1892s, as noted, had some parts marked. In conducting a reasonably thorough study of those guns I can detect armory fixes. On guns claimed to be "original."
Parts broke in service. Units had spare parts to fix them. The guns were repaired at arsenals. They were tools and repaired accordingly.
So if the Blue Book of Gun Values thinks somebody can detect an "original" gun they have access to chemicals and have partaken.
Hate for that to sound like a rant but it's kind of a pet peeve. I have quite a pile of original arsenal repair records here which have never been reviewed in the creation of the existing books. These records point to much more repair of those guns than was previously assumed.
So if it's a really good looking gun, it's probably fine.
Here is an example of a very nice 1898 Krag. Almost pristine:
http://www.gunbroker.com/Auction/ViewItem.aspx?
Item=152259629
That gun has the wrong rear sight. See what I mean?
Beautiful gun though. I should have bought it. I bid on it but was after another.
