It's a 57-D worth a nickel. I am unaware of any famous 1957-D doubled die Jefferson nickel. It's not on this list: http://koinpro.tripod.com/ErrorVarietyList.htm That doesn't mean it doesn't exist, but if millions of people have been looking at this coin for 50 years, it's likely that if there were a DD variety we would probably know about it.
The M and a few other letters are damaged, from contact with another coin or something else while it was in circulation. Not an error, not a doubled die......sorry
Look at all the letters close to the "M". They all have similar damage. Not as much perhaps, but, they are damaged in a similar fashion.
Hard for me to tell, from that image . But there is a DDR . You'll have to check OP . https://www2.briansvarietycoins.com/listings/cat/30