That makes sense. However, from Craig's Age Guide details:
"If the lid vent says WEBER in engraved font with an elongated b in weber, still small vent turn tab on lid, but now with wider dual turn tabs on the bowl vents and more familiar WEBER whitewall all plastic wheels it could be from or 1976-1977."
I have two 18" with the elongated b Weber. However, this yellow has the BAR-B-Q Kettle letter. I think this is model made during the transition.
I guess it is a 75 or 76.