The following photos are from the US Marine Corps Air-ground museum at Quantico. They were taken in Oct, 2001. Special thanks to Greg Balzer and Ken Smith-Christmas, the curator for arranging the visit.
Thanks to Grzegorz for identifying it. The gun is a 47mm (3 pounder) 5-barrel revolving cannon.
Knut Erik Hagen took these photos in March 2004 at the Tojhusmuseet, København (Royal Danish Arsenal museum).
Knut Erik Hagen took these photos at IWM London in July 2003.
Robert Horton notes: This is a French or United States model of the French 75mm field gun.
Knut Erik Hagen took these photos in March, 2004 at the Forsvarsmuseet (Armed Forces Museum), at Akershus Castle, in Oslo.
This is an Anti-balloon / Zeppeliner gun of French origin,model "Puteaux". Some were set up around Oslo in 1917.
It is French 75mm gun with carriage and axles adapted for mounting on an AA framework.