Coach builders of the day numbered their work in the same way as vehicle manufacturers numbered their vehicles so I would say that is a body (rear deck) numbering code from whomever made that body. I hope you rescued the badge?
What was the rest of the truck like?
G'day Cliff,
It had a very good horn and a exterior door handle until I took them off and paid for them. Body and tray of truck was sad. Badge was rescued.