The 15' Classic Aluminum Canoe is manufactured out of aircraft aluminum and heat treated in order to harden it for additional strength. These are produced in several thicknesses.
The lightest weighing in at 68lbs is the .040 gauge aluminum canoe.
The interior is not painted but is popular with rental operators and camps. They don't like the paint showing dirt.
The middle grade 71 lb one is .050 gauge aluminum and is painted grey on the interior with a couple extra ribs(as shown above). The paint acts as a non skid and helps wet feet not to slip as much.
The toughest of course is the .060 gauge canoe and it is for high use or whitewater situations, but the 74 lb weight is to be a consideration.
The canoe has stretch formed sponsons on the sides above the water line. These "safety foils" effectively give the canoe a wider profile for extra stability while keeping the streamlined profile during normal paddling.