I previously wrote about a mysterious "German SPAAG" that was shipped to the USSR for study along with the Maus and Sturmtiger. This SPAAG was likely the Kugelblitz. Unfortunately, I have not found any detailed study of this vehicle. The article in the Tank Industry Herald is incredibly brief.
"German SPAAG "Kugelblitz"
To protect tank columns on the march, German designers created a SPAAG that had mobility, firepower, and battle readiness speed required to escort tanks.
The chassis and hull of the new vehicle was taken from the PzIV tank, the most common German tank. To install a special rotating turret the Tiger tank turret ring was used.
As you can see in figs. 1 and 2, the gun shield is built like a sphere. It contains two 30 mm Rheinmetall MK-103 cannons and two AA sights (the guns are automatic and belt fed). The crew consists of two gunners (one aims vertically, the other horizontally) that are also housed in the ball mount and rotate with it. The design of the turret and gun shield allows the vehicle to fire at targets all-round with a gun elevation of up to 90 degrees. In addition, an MG-34 machinegun is installed in the hull. The crew consists of five men: commander, two gunners, driver, radio operator.
Three prototypes of this vehicle were built. Further production ceased due to occupation of the Ruhr area by the Allies, where mass production was supposed to have taken place. In parallel with prototype construction, a further modernization via installation of two more 20 mm autocannons was developed. To allow for faster aiming, the vehicle would be equipped with a hydraulic traverse system. These SPAAGs would use the 38D tank's hull and suspension.
These kinds of SPGs, despite comparatively weak armour (up to 30 mm) can successfully be used to protect tank columns on the march given sufficiently quick-acting autocannons and mobility."
Tank Industry Herald 1945, ##10-11 p. 35