It's traditional in the North American auto industry to introduce the new model year vehicles in the fall proceeding the calendar year designation, usually September. So yes, you have a very early '67 Cyclone. There are many exceptions to this, some cars are introduced earlier, for example the 1965 Mustang was introduced in April of 1964, some cars later if the new design is running late or just to make it stand out from the rest. It used to be a much bigger deal years ago for people to go to the local car dealer and check out the new models when they were introduced in the fall - people were much more easily entertained years ago than they are now lol. Ford would begin the last 6 digits of the Mercury VIN series with 500001 at each assembly plant ( Fords started with 100001 ) so your VIN should be pretty close to that number. The cars were not built in numerical order, so a car with a higher number could have been assembled before yours. The fact that your car was built before the scheduled build date illustrates how that happens, but also means you should have an early number. Comets and Cyclones were assembled at more than one assembly plant though and they didn't all necessarily start production on the same day.
