The Swedish Bofors company developed a sophisticated and very high-quality light anti-tank gun in the early 1930s, and found significant commercial success with it. A variety of countries either purchased the guns outright from Bofors or paid for licenses to produce them domestically. These countries included Denmark, Finland, Poland, the Netherlands, and Sweden itself. The largest number were in Poland (1200 or more), and there is speculation that some may have been sold to Spain during the Spanish Civil War (both these guns and a 40mm AA gun which definitely went to Spain were designated wz.36). A significant number were also captured and reused by German and Russian forces during WWII. On the Allied side, some of the guns were sold to the Sudan and used by British forces in North Africa (generally mounted on trucks).
The gun itself was an excellent design, capable of 12 rounds/minute of accurate fire and potent enough to deal with most of the smaller tanks in existence at the beginning of WWII. New tank developments made it obsolete, but it was at least effective against Russian light tanks (BT, T-26, T-28) in the Winter War if not the heavier T-34s. The gun has a sophisticated suspension system to help absorb recoil energy, and fired a 37x257mm shell with a 740g projectile at about 825 m/s (26oz @ 2700 fps). The action was semi-automatic, meaning that once fired, the action would recoil on the carriage, and automatically eject the empty case. It would then return to battery with the breech open, ready for a new shell to be loaded (in the video, the ejection mechanism has been disabled to help preserve the brass cases).