The Marder was a way of exploiting the obsolete Czech Panzer 38(T) tank and making it into a useful armoured vehicle. The Panzer 38(T) was a reliable and easy to maintain light tank but was surpassed by newer tanks in combat but it's chassis and engine proved perfectly suited as a basis for a wide variety of armoured vehicles. The Marder had an open topped compartment at the rear of the vehicle in which could be mounted a much larger gun than the turreted Pz 38(T) could possibly carry. In essenence it became a self propelled anti tank gun or tank destroyer. It could be used in support of infantry or tanks to give them some anti tank firepower. Usually they would be concealed and wait in ambush and then move to another position after firing, to avoid direct combat with tanks. The Marder III M, carried a 75mm PaK40 gun, which was powerful enough to knock out most tanks it would likely encounter.
This looks like an excellent kit from Hobby Boss, highly detailed with many parts. The tracks are individual links and the model includes a metal gun barrel and photo etch metal exhaust grill.