Pitcairn Aircraft Factory was located in Willow Grove, Pennsylvania (USA).
Pennsylvania is known as the Keystone State (the emblem on your original photo is a Keystone). It might be the Pitcairn aircraft logo or an aircraft owned/used by Pennsylvania.
http://impdb.org/index.php?title=File:Amelia00042.jpg
http://www.dmairfield.org/airplanes/NC6708/index.html