Congrats on a lucky find!
Mine was under the rug taped to the tunnel. Does yours have an early April date on the top right? Mine has a body number of 31556 with a mid-April date. I don't show that too often because it is likely the only remaining proof of authenticity left.
I mean....after reading some of the posts here from last week, even POP's are look upon as not being reliable proof anymore due to the almost perfect reproductions. So, IMHO, an UOIT is the next thing. I've had some people ask me about mine and I show an altered copy and I don't discuss paper weight or the fine print along the tractor feeds.