Buy Halo 5 at a military base, get a rare collectible

There's a nifty little collectible in specially marked boxes of Halo 5: Guardians, but there's also a catch: They're only available at U.S. military exchanges, where one must have the privilege to shop, typically as an active or retired service member, or the dependent of one.

A Reddit user found and posted this coin being solid along with the game, which launched last week. The coin is about twice the size of a U.S. quarter dollar, and on eBay is now listed from $33 to $99.

Microsoft confirmed to Polygon that the Halo 5 premiums are offered only in games sold at military PXes.

"Our U.S. retail team worked with the Army and Air Force Exchange Service on this," a spokesperson said. "We've done this in the past for big title launches as a gift with purchase (while supplies last)."

The coin's obverse depicts Spartan Locke and Master Chief; the reverse lists the nation's five armed services. eBay listings refer to it as a Challenge Coin, which is a type of military collectible that has become very popular over the past 25 years.

The video below shows off several game-themed challenge coins, ranging from Xbox One exclusives Dead Rising 3 and Sunset Overdrive to Destiny and Call of Duty: Modern Warfare 3.

Halo 5: Guardians launched Oct. 27 on Xbox One. Polygon rated it a 9, calling it "one of the most welcoming, competitive, balanced and fun games of the year."