Unlike many military items that claim they are WW2, this Howitzer is dated 1937 and was removed from a disused Soviet base near to Dukelska in Czech Republic. It stood as a gate guard for many years, this area was where the Soviets advanced through from southern Poland.
The barrels were either monobloc or built-up. To soften a recoil, a large slotted muzzle brake was fitted. The breechblock was of interrupted screw type, with forced extraction of cartridge during opening. A safety lock prevented opening of the breechblock before the shot; if there was a need to remove a shell, the lock had to be disabled. To assist loading when the barrel was set to high elevation angle, the breach was equipped with cartridge holding mechanism. The gun was fired by pulling a trigger cord.
The recoil system consists of hydraulic buffer and hydropneumatic recuperator. Each held 22 ltrs of liquid. The carriage is of split trail type, with shield and balancing mechanism. It has leaf spring suspension and steel wheels with rubber tyres.
During transportation the barrel would be pulled back. The gun could also be towed with the barrel in its normal position, but in this case the transportation speed was limited, about 4 to 5 km/h (compared to 20 km/h with barrel pulled back). The gun could be set up for combat in 8 to 10 minutes.
The 152 mm howitzer-gun M1937 (ML-20) was a Soviet gun-howitzer. The ML-20 was one of the most successful Soviet artillery pieces of World War II. Its characteristics positioned it between classical short-range howitzers and special long-range guns. It was in production from 1937 to 1946. The ML-20 saw action in World War II, mainly as a corps / army level artillery piece of the Soviet Army. Post World War II, the ML-20 saw combat in numerous conflicts during the mid to late twentieth century. The gun was in production in 1937-46. 6,884 guns were manufactured and about 4,000 ML-20S barrels for using in self-propelled guns SU-152 and ISU-152.
More information at: Russian Military