Can anyone advise if AD7811 always comes with an AD in front of the part number eg AD7811 on the topside body marking? or does it exist as 7811 as well. Pls note I'm not talking talking about the AD logo but the alphabet AD.
Look at pages 3 and 7 of the rev C AD7714 data sheet. It's there.
However, I would not do a new design with the AD7714; it's very ooooold.
Look at the AD7770 or AD7779.
If you need PDIP, then use multiple AD7822 or AD7811.