Thank you Tanker and Ralph. Using your information I found the French Wikipedia article on the 75. It has much more information than the English language wiki article, including a sentence or two on where the guns were made.
This gun is now at Harriston, Ontario at the War Memorial. It was allocated shortly after the war, sometime around 1920 give or take a year. Unfortunately there is no information in the records about the capture of this gun.
I am wondering if any of the German Landshippers can find anything about where and how Germany acquired this gun (or who was using it last and where). And I am wondering if any French Landshippers can say where this gun was being used when it was lost to the Germans.
I am going on the theory that this gun was captured by the Germans and then captured from them by the Canadians.