Well, it seems the provided context, which consists of an eBay link and the entire legal footer of YouTube, is about as helpful for identifying a coin as a screen door on a submarine. I can't tell you much based on YouTube's copyright policy, so let's set that aside and dip into some actual numismatic knowledge.
You're asking about the Kennedy half dollar with the dual date 1776-1976. This isn't a coin from the Revolutionary War that someone kept in their pocket for 200 years; it's the U.S. Bicentennial commemorative coin, struck in 1975 and 1976 to celebrate America's 200th birthday. It was part of a nationwide party that also involved tall ships and a whole lot of bell-bottoms.
The front, or obverse, features the familiar profile of John F. Kennedy, but with the special 1776-1976 date underneath. The real change is on the back, or reverse. Instead of the usual Presidential Seal, this coin sports a handsome image of Independence Hall in Philadelphia, the very spot where all the declaration-signing action went down.
Now, for the million-dollar question that's actually a 50-cent question: what's it worth? The U.S. Mint produced these coins in truly massive quantities, over half a billion of them, in fact. The standard circulation coin is made of a copper-nickel clad composition, just like a modern quarter. If you have one of these, it's worth exactly half a dollar. However, the Mint also made special collector's versions containing 40% silver. The easiest way to check is to look at the coin's edge. If you see a reddish-brown copper stripe, it's the common version. If the edge is a solid silver color, you have one of the silver-clad coins, which is worth a few dollars based on its silver content.
