What is the overall length of the canoe? Mad River made a 16’ Royalex Explorer beginning in 1975 until Royalex production ceased. But they also made a 17’ Royalex Explorere from 1983 to 1991. It is possible that the canoe has been rerailed or otherwise modified. The 16’ Royalex Explorers came stock with only a single center thwart/yoke, but the 17 footers (which were actually 17’ 2" in LOA) had a second thwart placed in the aft half of the boat. So your canoe has either had an additional thwart placed or is the longer version.
The Royalex Explorers came with either wood trim or synthetic gunwales and deck plates. The synthetic deck plates used by MRC usually had a circular logo molded into the top. I can’t tell from your photos whether that is the case or not.
I suspect that the canoe was repaired externally and internally after the hull wore through which happened due to abrasion in Royalex hulls. It looks like there is a mulit-laminate aramid internal repair in addition to an external aramid patch over a preexisting skid plate. Judging only from the photos it looks as if it was pretty well done and if the person who repaired it got a good epoxy bond to the ABS of the hull, it should hold up pretty well.
If the aluminum plate with the hull identification number has been removed, look at the interior up under the deck plates. The HIN was sometimes marked with a marker in that location before the gunwales and deck plates were added. The Royalex sticker was common on Royalex boats for decades and does not suggest a specific vintage. I suspect the Costeau sticker was added by a prior owner.