The Mystery Stone is on long-term view at the state historical society in Concord. It's been in their possession for quite a long time.
http://www.nhhistory.org/museumexhib...sterystone.htm
Rear view:
I'd be very surprised to learn it is an actual Abenaki artifact. After the stone's discovery in the 1800s, some researchers studied it and suggested the carvings could not have been rendered by the tools available prior to contact.