Thanks Trev. I had originally assumed that the 0.2.0 bit was referring to the number of axles. However, when I did a "search" and discovered the sort of equipment that Decauville produced I started to think that it could really have been an 0-2-0 in the Whyte system.
I had visions of a single axle propulsion device that was coupled to a wagon and relied on it for support.
John.