The DLC weapon will be located at the START or first checkpoint of each location. They're placed on a special stand or table.

Attack your opponents with the Sabre wz.1921!
It was introduced into the army in 1921 and used until 1939 as individual armament for soldiers of the mounted artillery squadrons, light artillery regiments, squadrons of the Border Protection Corps, tabors and “Krakus” divisional cavalry.