One of the documentation copy companies is doing copies of
"Wireless Sets No. 19, 19 H.P., 19/19, 19 H.P./19
in
Trucks, 15 cwt., 4x4, Personnel
and
Trucks, 15 cwt., Half tracked, Personnel
Fitting Instructions".
It covers the White Scout Car.
Alas I don't know which company it was and my copy isn't marked, but hopefully with the mouthful of the name you can track it down.