You have correctly deciphered your Hull Number. Mine has a similar plate at the rear of the cockpit, as it is also a 1971 from the Niagara on the Lake facility.
If you want to swap info on and experiences with the Mark I, shoot me an email [deleted]
C&C 27 Mk I, #45, Vermonstah
[There is one rule on this Forum: no soliciting of private responses via e-mail unless for the purpose of buying or selling something. When the conversation happens in the Forum, we all learn, which is the point of having a public Forum. Please read this explanation. - Admin]