This is a rare vintage original comic shop dealer's STAR TREK PROMOTIONAL DECAL/WINDOW CLING, which was designed to adhere to a comic book shop's window by static cling. That's why the lettering is backwards, and it measures about 13 inches by 10 inches. It was NEVER FOR SALE to the public, very few were ever made, and most have been lost or destroyed by now, making it even more scarce.
This DC Comics promo window decal has never been used, but does have a few "dings" (especially around the corners) from storage. It's still a very hard collectible to find, because of the few of them made, most have been used, lost, or destroyed by now, making them even more scarce.