The eBay listing referenced above has a number of inaccuracies in it (unfortunately, a common occurrence for that particular seller) -- the medals are not antique-finished, they're not layered in gold and they weren't a Smithsonian Institution program. Here's a bit of accurate info on your medal and the series of which it was a part.
The medal you have was not part of a philatelic-numismatic cover (PNC). This medal was sold two ways: in a PNC and individually in a black plastic case. You can always tell the difference between the two by checking the medal for a date. Those sold in the PNC were not dated, those sold in the plastic case were. Your medal bears the date "1972" and so it was one of the cased medals.
These medals were sponsored by American Revolution Bicentennial Administration (ARBA) and were struck by the US Mint. The ARBA medals were issued between 1972 and 1976; the bronze medals were available individually for $3.50 and in the PNC for $5.00. Beginning in 1973, the medals were also available in sterling silver; they sold for $10.00 in 1973, for $15.00 1974-76.
Washington was featured on the obverse of the medals in 1972, Patrick Henry and Samuel Adams in 1973, John Adams in 1974, Paul Revere in 1975 and Thomas Jefferson in 1976.
All of these medals are common in the US, available at just about every small or large coin show and, of course, are always available on-line.
Hope this helps! Let me know if you have any additional questions.
Collecting history, one commemorative coin (or medal) at a time!
Original content (c) Commems, 2012-2014