Many years have this sort of thing listed as a doubled die eye, but I don't find one for 74D. Sure looks like it.
Well, the doubled eye is shaped like another eye...kinda like this < What you have is a small die chip.
Thanks. Have a look at http://www.coppercoins.com/lincoln/dietype.php?date=1956&die_mint=d&die_type=do&page=0 Most of those just look like another lid lower down, like this one.
I think that using diagnostics of a 56 to attribute a 74, or any year other than 56 for that matter, is like using a pirate's Caribbean treasure map to find the 'X' in your backyard.... You will only be needlessly frustrated.
then you need to make an investment in it, and your belief, by sending it to a specialist/attributor and hope for the best. Believe me, I'm eager to find a discovery piece myself. There are folks here who have been as lucky. One day..... good luck!
Perhaps I should just make a note and save it. Would cost more for attribution than the $3 coin it would become
But think about the glory of having that coin permanently associated with your name on a website! Plus, submitting it to an attributor would let you know FOR SURE what it is. I personally think it is either a die gouge or perhaps a die chip.