Question: Sturmgeschütz III was built on the chassis of a tank developed in Germany in what decade?

Context paragraphs:
Jagdpanzer IV: The "Jagdpanzer" IV, Sd.Kfz.  162, was a German tank destroyer based on the Panzer IV chassis and built in three main variants.  As one of the casemate-style turretless Jagdpanzer (tank destroyer, literally "hunting tank") designs, it was developed against the wishes of Heinz Guderian, the inspector general of the "Panzertruppen", as a replacement for the "Sturmgeschütz III" ("StuG" III).  Guderian objected against the needless, in his eyes, diversion of resources from Panzer IV tank production, as the "Sturmgeschütz III" was still more than adequate for its role.

7.5 cm KwK 40: The 7.5 cm KwK 40 "(7.5 cm Kampfwagenkanone 40)" was a German 75 mm Second World War era vehicle mounted gun, used as the primary armament of the German Panzer IV "(F2 models onwards)" medium tank and the Sturmgeschütz III and Sturmgeschütz IV assault guns "(F models onwards)".

Sturm-Infanteriegeschütz 33B: The Sturm-Infanteriegeschütz 33B was a German self-propelled heavy assault gun used during World War II.  A new, fully enclosed, and heavily armored boxy casemate superstructure was built on the chassis of the Sturmgeschütz III.  It mounted the improved sIG 33/1 infantry gun, offset to the right side, for which 30 rounds were carried.  It could only traverse 3° left and right, elevate 25°, and depress 6°.  A MG 34 machine-gun was fitted in a ball mount to the right of the main gun with 600 rounds.  Its traverse limits were 15° left and 20° right, and it could elevate 20° and depress 10°.

Medium Mark III: The Medium Mark III was a medium tank developed in the United Kingdom during the post war.  The tank was unsuccessful with only 3 built.  The design did not directly derive from earlier Medium Mark II tank.

Tank EX: Tank Ex, or MBT Ex, was the code name of the main battle tank developed by the Indian Defence Research and Development Organisation (DRDO) in 2002.  It was rumoured the tank would be called "Karna", after one of the heroes of the Indian epic "The Mahabharata".  Tank Ex was developed as a second attempt after the development of the Ajeya (an upgraded T-72) by DRDO in order to capitalize on the technology developed for that project.  It underwent six months of trials, but was subsequently rejected by the Indian Army.  At least two Tank Ex prototypes were built.

DRDO light tank: The DRDO light tank is a tracked amphibious light tank developed in India by DRDO.  It is based on the "Sarath" chassis, a licensed variant of BMP, built by the Ordnance Factory Medak with a French GIAT TS-90 turret and 105 mm gun.  This vehicle is designed to carry high caliber weapons without sacrificing mobility.

Panzer III: The Panzerkampfwagen III, commonly known as the Panzer III, was a medium tank developed in the 1930s by Germany, and was used extensively in World War II.  The official German ordnance designation was Sd.Kfz.  141.  It was intended to fight other armoured fighting vehicles and serve alongside and support the Panzer IV; however, as the Germans faced the formidable T-34, more powerful anti-tank guns were needed, and since the Panzer IV had more development potential, it was redesigned to mount the long-barrelled 7.5 cm KwK 40 gun.  The Panzer III effectively became obsolete in the anti-tank role and was supplanted by the Panzer IV.  From 1942, the last version of Panzer III mounted the 7.5 cm KwK 37 L/24, better suited for infantry support.  Production of the Panzer III ended in 1943.  However, the Panzer III's capable chassis provided hulls for the Sturmgeschütz III assault gun until the end of the war.

Sturmgeschütz III: The Sturmgeschütz III (StuG III) assault gun was Germany's most-produced armoured fighting vehicle during World War II.  It was built on the chassis of the proven Panzer III tank, replacing the turret with an armored, fixed superstructure mounting a more powerful gun.  Initially intended as a mobile assault gun for direct-fire support for infantry, the StuG III was continually modified, and much like the later "Jagdpanzer", was widely employed as a tank destroyer.

Jon Phillips Armor Collection: The Jon Phillips Armor Collection is a private collection of armored vehicles owned by Jon "Welderbeast" Phillips, a mobile welder and World War II vehicle hobbyist from Hoo, England.  The collection includes a replica Panzerkampfwagen III, a restored original Sturmgeschütz III Ausf.  D, and a restored Volkswagen Schwimmwagen.

Patagón: The "Patagón" tank is a light tank developed in Argentina during the early 2000s, expected to enter service with the Argentine Army.  It is based on a SK-105 Kürassier chassis with a refurbished AMX-13 turret.  The project was cancelled in late 2008.

Supporting paragraphs: Sturmgeschütz III Panzer III
Answer: 1930s