The angle iron rails at the edge above the tracks would identify this one as having been in one of the Canadian Infantry Division's Support Battalions as part of a 4.2" mortar platoon. Course they didn't have wooden bodies back then
I've also never seen wheels with the round holes so not sure what they originated on unless they are late patten T-16 solid disc wheels with lightening holes bored into them. Or holes bored into them to make them appear closed to the stright spoke or curved spoke patterns.