This is a Forster Headspace chamber gauge, for the 6mm Remington (aka .244 Remington) chambered rifles. It is the Field version, which is the longest of the three standard gauges (if your bolt closes on a No-Go gauge, it may still be serviceable, if it closes on a Field gauge, it is unsafe to fire)...
It is new in the package, unused... I purchased it thinking it was a .243 gauge (the had the .243/.308 Go and No-Go gauges right there on the shelf with it, and I grabbed it without looking LOL... little shop is 5 hours away, so cant return it)..
I am selling this for $20, and I am open to trades. I still need a Field gauge for .243/.308, .223 Rem/5.56, and a few others, as well as other parts or tools.
E-mail is the fastest way to contact me, G2Gunsmithing@Gmail.com