John:
Don't have an answer for you...but you may wish to contact the American Aviation Historical Society at: http://www.aahs-online.org/
AAHS, like IPMS/USA, is a non-profit run by volunteers, so their response can sometimes take a while and since they are only in "the office" on Wednesday afternoons.
They produce an excellent Journal and are now converting thier photo archives to digital to ease access.
In the mean time, I'll keep digging through my souces.
It could be that the four photos illustrate more then one aircraft of the same type. The engine appears to be a Wright engine.
Nat