Pat pending vent, so I don't know what year it actually is, any guesses?
I think it depends on the wheels.
Metal wheel with rubber tread would be '68 I think.
Plastic wheel with rubber tread '69 or '70.
All plastic wheel '71.
I could be wrong on those dates, but it will give you an idea.
My Avocado has the plastic wheel with rubber tread, and I think we pinned it at '69 or '70.
Great looking grill regardless of age.