Thanks, David. I went through that page and it makes sense.
It's actually a 1965 S1
So what we have is a car built and registered in 1965 , based on the last letter "C" -Thanks Peter
Then the car looks to have been picked up in Coventry and driven back home to Italy where the owner lived. I'd love to get a tag number for Italy. Would the tag have changed from the Reg numbers issued at Coventry? I've emailed the Italian dealership...we'll see if they respond.
Thanks for all the help everyone!