The 155mm wz. 17 was the Polish designation for the French 155mm C mle 1917 S howitzer designed by Schneider. These guns were acquired by the Poles from the French at the end of the First World War.
In essence, the 155mm C mle 1917 S howitzer was a 155mm C mle 1915 S howitzer fitted with a different breech mechanism to accept a bagged propellant charge rather than a cartridge contained propellant. The French made the switch due to the high costs involved in manufacturing the brass casings for the 155mm C mle 1915 S howitzer.
At the start of World War Two, the Polish Army had over two hundred of these guns in service with the Heavy Artillery Batteries of the infantry divisions and like most equipment from armies opposing Germany; they also saw service in the German Army as the 15.5 cm sFH 17(p) after the fall of Poland.