This vehicle was developed from the type 89 medium tank using a slightly modified suspension. The original designation was "Soko Sagyosha" meaning "armoured working vehicle", short SS.
It was originally intended as attack vehicle against soviet border fortifications. Around 120 vehicles were built between 1931 and 1940 in five basic versions:
Version Ko = A:
additional armour plates on each side and a wire clearing bow attachment, only one flame thrower port in the bow
Version Otsu = B:
A flame oil tank in the rear and additional tanks between the suspension parts, large quadrangular cupola on the forward superstructure and a smaller circular cupola on the rear superstructure, three flame thrower ports in the bow, three return rollers
Version Hei = C:
a small hemispheric cupola on the forward superstructure, again additional armour plates in each side, one MG-port and one flame thrower port in bow and each side
Version Tei = D:
a small circular cupola on the forward superstructure, again additional flame oil tanks between the suspension parts instead of the armour plates, modified frontal armour, slightly modified suspension
Version Bo = E, final version:
slightly higher forward cupola with an upward hinged visor port, modified frontal armour with a large two-part door between the attachment points for the explosive charge, again modified suspension with only two return rollers, no fuel oil tanks between the suspension parts
Several exchangeable service kits could be attached. The mine clearing device mentioned above, a wire removing kit and an explosive charge could be mounted on the bow. The rear flame oil tank could be exchanged with poison gas and disinfection fluid tanks and also with a large trench plough. On the upper superstructure a 6 m scissor bridge, a 7 m normal bridge, a crane or a smoke laying mechanism could be attached.
Until 1941 the vast majority of the available SS were attached to the 5th Independent Engineer Regiment which was stationed in Manchuria. The remaining vehicles were attached in small numbers to several engineer formations and used in China. From 1942 the vehicles were attached to the four newly organized armoured divisions, mainly for bridgelaying purposes.