A mystery - fun.
Do you know the S/N that might/should be on the rating plate? That would provide some hints. I keep a list of S/N's, the earliest is 418950, reported to be a 1966 (but not confirmed).
If "MC" is Michigan, (I would have picked Neb from the posted chart and comment but) - how long are MI stickers good for? and how would a '58 sticker get on a newer boat? Here in MN they are good for 3 years, so if someone was trying to "catch up" their registration, I could see a '58 sticker on a '60 or maybe '61 boat.
And the paper work, again, I don't know what MI has, but here in MN we have both a registration and a title used for boats.
To use a boat on MN waters, there has to be a sticker, either MN or a "home" state. Registering a boat lists it with our DNR and a/the sticker is given that goes on the boat. The info on the registration is provided by the owner (or seller/dealer) and can be incorrect (it's not checked, our DNR cares little about the craft and more about that they know about it and get the fee).
If one has a large boat, then a title is also often provided, similar to a vehicle title to prove ownership and to transfer ownership.
(I have had a number of boats and lots of canoes, all registered and with stickers. Non have had titles.)
The point of this is info on state paperwork can often be wrong.
Oh, you might also check out that Starcraft Club previously mentioned, they may have build/date info.
Dan