Button id

[Chief901270]

I need help identifying this.....notice the back marking

 

Amazon Forum Fav 👍

DR.ÖTEK Metal Detector, Waterproof Gold Detector, Pinpoint & Terrain Modes, Professional Metal Detector - Grab it through Amazon!

[nhbenz]

I'd say it's a post-WWII Cavalry collar disc, missing the pins. This type is shown at the bottom of this link: Dating Metallic Insignia: Collar Disks

 

[AlienLifeForm]

Interesting that is has a masonic stamp on it.