Hi, yes you are correct 15 cwt is 3/4 Ton. The Army here called the small car type utilities, 12 cwt models. The US 1/2 Ton model, they classified as 15 cwt ... don't know why. The US 3/4 Ton they classified as a 1 Ton. This model has 17 inch wheels and heavy duty rear springs.

This pic is a car type 12cwt utility.
Attachments

1940 Canadian Chevrolet Series 13 (1/2-t) utility (Australian)
Lots of history here!
Read ot all in the DITY