I'm afraid my in-depth knowledge of Hug trucks is woefully inadequate. I know they built 4,014 of them in total from 1921 through 1942, and they made their name on the heavy-duty "Roadbuilder" model for the construction trade. They called their over-the-road lne of highway trucks the "Xpress", and I think that's what the unit pictured would be. The only model number I can find in reference to a COE unit like the one pictured is a Model 16, which is a 10-ton unit.
Best I can do.