Early models had bolted on supplemental armor on the front, with later models having it welded.3 Later models had the driver's binocular vision device removed.3 Late models had the ventilator mounted on the rear wall of the superstructure, whereas the early models had it mounted in the roof.3
A new commander cupola with 8 periscopes was added. A folding shield for the machine gun was installed in front of the loader's hatch on the roof.3,4
The sides of the superstructure were slanted and slanted plates were installed to protect the panniers. Most had Schürzen installed to protect against hollow charged weapons.3,6 Some also had Zimmerit paint to help against magnetic mines.3,4
The coaxial machine gun wasn't added until early 1944. In late spring 1944 a Nahverteidigungswaffe (close-in defense weapon) and a remote controlled machine gun in the roof was added.
Had commander's cupola3 with 7 episcopes.4 No box shaped projections on the sides of the superstructure.3 165 PzKpfw III Ausf M chassis were used for the StuG Ausf G and 173 PzKpfw III that were returned for overhaul during 1944 were converted as well.
Hitler wanted 220 built every month by June 1943.5 He then raised it to 300 per month in 1944.5 These goals were exceeded by the factories.5
Sturmgeschütz III Ausf G:
Sturmgeschütz 40 Ausführung G with Saukopfblende: In February 1944 the Saukopf (pigs head) mantlet was being used.5 Had Schürzen, and most with Zimmerit, installed at the factory.3
Munitionspanzer auf Fahrgestell Sturmgeschütz III Ausf G: In 1944 and 1945 some StuGs were field converted in to ammunition carriers by removing the main armament and using an armor plate over the aperture.
Vehicles issued to Funklenk Kompanien (Remote Control Companies) had an additional radio aerial installed on the left front of the fighting compartment.