I was quite a muscle car enthusiast back then. The '69 as I recall had a long production, not ending till close to the end of '69....which was unusual as usually new year cars came out around Sept.-Oct.
The 70 Camaro was an all new body style and came out in early 1970....kind of late, when compared to how model years came out back then. The Mustang was one of the first cars to come out at an odd time...April in it's case and it was marketed as a 1964 1/2 car. Some were registered as 1964's...some 1965, depending on the jurisdiction.
Think the first '70 1/2 Camaros I saw must of been around Feb- April of 1970.
I have a ' Matchless motorcycle manufactured in London, England in August 1967. It was sent to the states to be sold as a 1967 Matchless. It didn't sell and was later part of a bunch of Matchless new, yet unsold, motorcycles bought by a Canadian dealer and shipped up here.
It was sold in 1969 as a new 1969 motorcycle. According to my provincial registration it is a 1969 motorcycle...but according to it's serial number it was made in August, 1967 and a Matchless expert told me it is really a 1967 model.
What I'm saying is that with some vehicles ...they were classified as the model year, according to when they were sold. I think things and procedures were not as tight in certain jurisdictions, back then....over 40 years ago