Excellent picture, excellent place for window shopping!
To me it looks like one of many variations of a theme Vickers Amstrong manufactured to sell their tracked tractors to military and possibly civilian users.
An exmaple of such a tractor is the Fighting Tractor -
see Overvalwagen.com > Tractors. Most likely a one-off, built for testing in the Netherlands East Indies, but they ended up buying Vickers Utility Tractors. Most likely this one was based on
Vickers Amstrong's D50.
Hanno
Edit: while I was looking for pictures of the Fighting Tractor Richard posted the right answer
