Hello,
The overvalwagens were probably designed at the Artillerie Inrichtingen (KNIL Art. Workshop) in Bandung, Java.
That was no coincidence as the Artillerie Inrichtingen in Holland had designed several armoured cars in the interwar period.
They used GMC chassis in the late twenties and Morris chassis in 1935. The cars were 4x2 and used mainly for internal security purposes (for instance during the Jordaan-revolt in Amsterdam).
Here's some pics from a well-known source on the internet:
http://mailer.fsu.edu/~akirk/tanks/hol/Morris.jpg
http://mailer.fsu.edu/~akirk/tanks/hol/GMC.jpg
Kind regards,
Nuyt