My canoe is a 1965 Richardson Aquacraft 16 foot Manitou 66. The SN is 3029 if that is of any use. It was a pricey canoe. $325 (with two paddles) in 1965, $25 dollars more than a Grumman.
I do have the 1965 catalog.
When it describes the canvas covered models (Tripper, Lightweight, Voyageur, Camper) it refers to "Narrow cedar planking with machined half check on edges to form tight overlap joints to prevent sand from working under the canvas to prevent wear."
Where it describes the cedar strip models (Manitou, Regatta) no mention is made of the way the strips are joined.
Since my canoe is a 66, and sold in 65, I'm not sure that the 66 refers to the build year.
Lapped construction is mentioned for boats.