Original Fender I.D.(65-66)?

Hello Gang,
I have a guy locally who claims to have a 65/66 Ford, OEM / NOS (Original Equipment Manufacture / New Old Stock) Fender for sale.

I know my one original fender on my car, has a date stamp on top of the fender (you can see it when you open the hood). My other fender is a aftermarket (can you say Taiwan) it’s fit is not the greatest and has NO date stamp.

I do not know if FORD put date stamps on all of there 65/66 Fenders. In other words, It is my understanding, that a Manufacture would produce sheet metal / fenders, for the Factory to build cars. They would then, punch out a certain amount for the collision industry / Body shops ( I do not know if these had date stamps on them).

I have 4 questions:
How do I.D. the Fender to know it is a NOS from FORD (should it have a date stamp, color of primer, ect) ?
Does any one have a website or information on decoding the date stamp on the Fenders?
Anyone have a idea what a Original NOS 65/66 FORD Fender would (ballpark) be worth?
Can anyone tell me if they have tried a Dynacorn (or other company) fender that they like the fit on?

Thank You in advance!

Hey Horse Sence

THANK YOU for the good info! Now that you mention it, I recall my buddy's dad had a old dusty Ford (?) quarter panel in his garage ( it was not for a mustang) in the mid 70's. It was in red/orange primer and I do remember yellow numbers that looked like they were stenciled or stamped on it. I guess I'm so conditioned seeing the black e coat on every thing now days.​

It would be nice to know or have a list on best fitting after market panels. I have seen / heard mixed reviews on Dynacorn parts. I can only assume Scott Drake and Dynacorn parts are still made over seas, who knows maybe the same factory is punching them out for all U.S. venders? Thank you again for your info!