This is Miniart's excellent Sturmgeschutz III pre-production prototype "O-Series". Five Panzer III Ausf. B tank hulls were pulled from the ordered production run to build mild steel prototypes for a self-propelled 75mm gun for infantry support. Incidentally, the five leftover Ausf. B turrets from these vehicles were later mounted on Ausf. D chassis and used in service.

The complex and somewhat fragile suspension evolved until an acceptable design was found with the Panzer III Ausf. E, which became the design going forward for thousands of gun tanks and assault guns in the Panzer III series.

Because these O-Series prototypes were not constructed using armour plate, they were not suitable for combat, but used for crew training in Germany.

I built this kit out of the box as it really doesn't need any aftermarket items. My build portrays one of these early prototypes in 1940 at training grounds in Juterbog.

A link to my build log is here: https://www.track-link.com/forums/site_blogs/55007.