And then, there were seven...
I've been doing some research for grant applications to help fund the bridge project. We've consistently used the language adopted by the 2009 Historic American Engineering Record report that states that the "Moose Brook Bridge is one of eight boxed pony truss bridges remaining in North America."
I have since discovered that one of the two bridges of this design in Quebec, Covered Bridge # 61-02-P1 Pont Blanc over Deception Creek, burned and collapsed sometime before November 2016. FWIW, I also found a picture of the other Quebec bridge - and it is in very poor condition.
This gives us all the more reason to preserve this important bridge.