Roll marks on slides and/or frames

Glock logoThis is a living post and will be updated as I get more info.

Here is information about the various roll marks you may see on Glock barrels, slides, and/or frames.

The pentagon indicates polygonal rifling, which all Glocks use. A pentagon without a dot in the middle means the barrel is from grade 5 steel. Pentagon with a dot in the middle indicates grade 6 steel. Neither symbol has anything to do with +P and/or +P+ compatibility. For +P and +P+ info, see The Austrian government eventually required the 3D in the oval, which replaced the pentagon symbols. NIST (National Institute of Standards and Technology) created a 3D ballistics database for research to positively identify bullets fired from specific barrels. The 3D database will help draw positive matches between a fired bullet and the barrel it was fired from. Barrels marked with a 3D are in the database. Ballistic experts can strategically identify the correct source, but it’s not 100% accurate. For more info about the database, see It’s important to note that the evolution of these symbols should not be interpreted as there are issues with the components with previous marks.

The “AT” indicates it was made in Austria. Newer barrels made in Smyrna, GA have a “US” and a little outline of the state of GA.

From 1982 to 1991, Glock 17 pistols were assembled & test fired in Austria. (Later pistols were also assembled and test fired at Glock Inc. in Smyrna, GA.) Those barrels have an eagle roll mark. The eagle with the number 2 in the center is Austria’s coat of arms. The number 2 in the center of the coat of arms means it was proofed at the firing proof house in Vienna, Austria. You’ll also see this mark on frames from the same period.

The ‘NPv’ is the Vienna proof house roll mark for ‘smokeless powder proof for parabellum pistols’. The pistol was tested using a round loaded to at least 130%. Normally, Glock guns are tested with 120% loads. The markings are proof marks and inspectors marks as required on Austrian pistols that they met the 130% requirement. Many of those NPv marked guns have “Glock Inc, Smyrna GA” stamped on the bottom of the trigger guard.

Sometimes, you’ll see three letters after the NPv on Austrian made barrels. Those are date stamps to indicate when the BARREL was test fired (note that does NOT necessarily mean when the pistol was built). Eventually, Glock did away with those three letter codes. Unofficial information I have to decipher those three letter codes that are on the barrel (not the serial number) are:

The first letter is for the month:

The last two letters are for the year:

For those with the ‘CIP over N’ roll mark, see and

Gen 5 pistols have a ‘5’ to the right of the ‘3D’ mark on the barrel. Some ‘M’ guns have a ‘5M’ to the right of the ‘3D’ mark. Others have just an ‘M’ or a ‘5’.


10 Replies to “Roll marks on slides and/or frames”

    1. If the serial number on the frame matches the barrel it’s original are you worried it’s a p80 or something made to look like a oem Glock or what I’ve never heard anyone ask if their Glock is original or not they’re not like historic pieces or anything so it doesn’t really matter lol

      1. Well, there are collectible Glock pistols that go for substantial prices. Ensuring those are original and authentic is critical in that aspect.

      1. Mine does. I was issued the 17m from my department. It was a prototype from glock. IMPD. I heard new jersey state p.d. also received the prototype 17m and the FBI the 19M.

  1. Hi, thank you for the information. My name is Manon Visser, I am an intern at the division Weapons & Munition at the Dutch Forensics Institute and I am curious about the markings. Could you maybe elaborate on the difference between the steel grades? I can’t seem to find the difference between grade 5 and 6.

    Also the 3D in the oval, is that linked to the database? And does that mean that it also has polygonal rifling?

    I’d like to hear your answer!

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