Yes, a French 25mm cannon.
From the internet:
http://weaponsman.com/?p=35291
French WWII 25mm SA.L Mle 1937 anti-tank gun, serial number 566. This anti-tank gun was built in 1939 by the French design & manufacturing company, Atelier Puteaux, and is marked accordingly: “A.PX 1939”. These guns were manufactured and used by the French, but they were also captured and used by the Nazis, who gave them the designation: 2,5cm PaK 113(f). A quantity of the captured guns were sold by the Germans to Finland, who gave them the designation: 25 PstK/37. The gun has a muzzle velocity of 3150 feet per second, and is a very accurate weapon.
I recall seeing one for sale in the EE a while ago.