...the rifles on the coin appear to be Model 1903 Springfield's (see pic below)
issued to US troops during the First War. It saw service throughout most of the first half of the twentieth century, being replaced during World War II with the M1 Garand.
<img src="http://www.surplusrifle.com/1903/graphics/full.jpg" alt="" />
I haven't found a match for you, but the info on "challenge coins" below is interesting. Note, the blanks left on the challenge coin below for service information to be engraved. Very similar to yours.
From the link below:
>>> Challenge coins have become as diverse as the military units that they represent. Challenge coins are a relatively new U.S. military tradition, but they are said to have their roots in the Roman Empire, where coins were presented to reward achievements. What some believe to be the first military unit challenge coin came about during World War I, when a wealthy young lieutenant in a flying squadron ordered medallions struck in solid bronze carrying the squadron emblem for every member of his squadron. He actually carried his medallion in a small leather sack about his neck.
The story goes that after acquiring the medallions, this pilot's aircraft was shot down behind enemy lines and he was captured by a German Patrol. When captured, the Germans took all of his personal identification except for the small leather pouch around his neck. In the meantime, he was taken to a small French town near the front. Taking advantage of a bombardment one night, the captured pilot donned civilian clothes and escaped.
He succeeded in avoiding German patrols and reached the front lines, where he eventually stumbled into a French outpost. Unfortunately, the French in this sector of the front had been plagued by saboteurs. They sometimes masqueraded as civilians and wore civilian clothes. Not recognizing the young pilot's American accent, and with no identification, the French thought him to be a saboteur and made ready to execute him. Just in time, he remembered his leather pouch containing the medallion. He showed the medallion to his would-be executioners. His French captors recognized the squadron insignia on the medallion and delayed his execution long enough for him to confirm his identity. Instead of shooting him, they gave him a bottle of wine.
Back with his squadron, it became a tradition to ensure that all members carried their medallion or coin at all times. This was accomplished through a challenge in the following manner--a challenger would ask to see the coin; and if the challenger could not produce his coin, he was required to purchase a drink of choice for the member who had challenged him. If the challenged member produced his coin, then the challenging member was required to pay for the drink. This tradition was continued throughout the war and for many years afterward by the surviving members of the squadron.
In the U.S. military, the tradition goes back to World War II soldiers who were given a coin when they mustered out of the service. Originally, the coins, which bear the unit crest on the front and whatever design the unit wants on the back, were given out by commanders and sergeants major to recognize outstanding acts performed by soldiers in the course of duty or to a soldier when he retired. They were intended to boost troop morale and to build unit cohesion.
It wasn't until the Vietnam era that a "challenge-response" was added to the tradition of giving unit members a coin. The initial challenge was to prove membership in a particular unit by producing the unit coin. That was followed by the addition of the requirement to "buy a round" if a soldier didn't have his coin. In the Airborne, you were given the choice of "buying a round" or "performing 10-pushups" on the spot, whenever the challenge occurred. In the mid-1980s, many other military units and organizations started minting challenge coins. <<<
