It's a camera/logbook cache named after UMass Transit Service (which operates most PVTA buses in the Amherst area). Has bus stuff: PVTA notepads, PVTA pens, PVTA magnets, and cardboard PVTA bus piggy-banks.
Make sure you check out the view North of the valley from the second overlook (it's only another 100 ft up the path from the first overlook).
Good luck!
Also, special thanks to Western_Mass_Clan for checking in on the cache!