penny loafer,
Take a look at the pictures in other threads that Coop has posted of the 1969 S
DDO Lincoln Cent. Yours would have to match exactly. It can't just be sorta, kinda, like it:-) It has to be 100% identical or it is not the doubled die.
Machine Doubling can effect anything anywhere at anytime. In other words, The mintmark not being doubled helps when you have the doubled die. The mintmark can also show no doubling at all on a coin where the date is machine doubled.
Good Luck. If you can scan the coin on a flatbed scanner, or take a picture of it with one of the newer phones, we can probably help you to know if it's a good one.
Thanks,
Bill