Ww2 medalion

What you have here is a WWII Veterans 'Challenge Coin'.  These coins have traditionally been commissioned by individual units throughout all branches of the military, and given to members of those units who served during any given time period.  Units typically release a new coin every several years or following major campaigns.  As for this specific coin, it is from the 52nd Armored Infantry Battalion, who during WWII, were 'attached' to the 9th Armored Division, as reflected on the reverse of the coin.  As indicated on the coin, the unit saw significant combat action at both Bastogne and the Battle of Ramagen, where the 9th Armored Division is credited with capturing the Ludendorff Bridge minutes before it was to be destroyed by the Germans.  The Ludendorff was the only bridge left standing across the Rhine, and its capture is credited with shortening the war significantly.  If this coin belonged to your great grandfather, I would assume that he served with the 52nd during WWII, and was presented with this coin upon his return to the States, along with the rest of the men who served with him.  In keeping with tradition, your grandfather would likely have carried this coin with him in anticipation of meeting with other veterans from the war, especially others from within his own unit.  Upon meeting with a fellow veteran from one's own unit or any other unit for that matter, one would often be 'challenged' to produce their unit's coin, hence the name given these coins.  If unable to produce one's own coin after being challenged, you would be obligated to buy the other guy a drink.  If you could produce your own coin upon being challenged, then the guy who initiated the challenge would be the one who would have to buy the other a drink.  This tradition isn't quite followed as closely these days, but it was a much bigger deal with many of the old timers back in the day, especially following the war, and I would venture to guess that your great grandfather likely carried this coin with him wherever he went for many years.

The 52nd Infantry is still around today, although it has undergone many redesignations over the past decades, as most units have.  Today the 52nd Infantry Regiment has two active companies assigned under the 25th Infantry Division, with one in Alaska, and the other in Hawaii.

Today there are an infinite number of coins out there from every possible unit, most reflecting the past decade of war, and they can be easily found for $10-15.  The older ones are far more rare, however they have not really become a sought after collector item as of yet outside of the military community, and they can usaully be found for only slightly more, $20-25 online.  Yours does not appear to be made of silver, as few if any ever were, it is most likely bronze or nickel with a bronze finish. Something like this is far more valuable as a family heirloom and should be passed down to family members with an appreciation for what your great grandfather did to earn it.

http://armedforcesmuseum.com/did-the-military-challenge-coin-originate-during-wwi-or-wwii/