Quote:
the post office clerk mentioned she had to ask her supervisor if this "stamp" was real and could be used, or just a label.
Just another clueless postal clerk that doesn't know or care to know about stamps.
Don't worry. The stamp IS REAL and may be used for first class postage.
Here's the official USPS sales page for that stamp issue, where they are charging $7.04 for 16 stamps at 44 cents each, which has to include the center stamp to make the 16th stamp from that sheet:
https://shop.usps.com/wcsstore/Post...htm/gogreen/ Actually, there was a small controversy about this center stamp prior to its issue. There was a preliminary design of the sheet of stamps that was publicized like this:

However, a close eye will reveal that wasn't the center stamp actually issued. The final version that hit the post offices contained the words "USA" on the last line of the text, a step necessary to differentiate a label from an actual stamp. So the final sheet of stamps actually looks like this:

As I understand it, the story goes that the intent of the USPS was to issue 15 stamps and that center one was to be designated as a "label". After some consideration, however, the USPS [correctly] figured that the general public would mistake the label for a stamp and use it on first class mail anyway, which would result in a financial loss of value to the post office, so to remedy the problem, they simply added "USA" to the center stamp and voila! We have a legitimate Forever stamp that is now included when you buy a sheet of these stamps.