Tools
Serial numbers and date codes
Some makers stamped the date on the object. Some numbered in sequence and published the list. Some did neither — and where that is the answer, we say so. Pick a maker and this turns what is engraved on your camera or lens into a production date, with the source it came from so you can check it.
A number outside every known block returns “cannot date”, never a guessed year.
Camera makers
Lens makers
These date the lens. A camera cannot be older than the lens on it, but it can be a good deal younger — so a lens date is a floor and a cross-check, not the camera’s date.