One of the things I have come across with research is that for some machines, even when produced in a reasonable quantity, very few examples have managed to survive into preservation. It looks like the Nu-trak tractor is one of those machines.
As you’ll already know there is actually very little information about the Nu-Trak. I did find some bits though such as in 1949 in ‘The Commercial Grower’ magazine: “Recently introduced machinery included the Nu-track tractor made by R. Bradford, London, and obtainable from Frank Bird (Engineers) Ltd., 26, Vachel Road, Reading. A small hand tractor, it is balanced on a single narrow caterpillar band placed centrally under the machine, which gives grip, and it is powered by a 880 c.c. engine. Price is £128.”
There is a Dutch magazine called ‘Landbouwdocumentatie’ and in 1949 ran a short description of the tractor so I wonder if any made their way to Holland?