1999 Penny - the left side (left of lincoln's head) is missing the rim. Is this a strike error or general wear?
It is quite possibly a tilted die strike which can leave weakness of the strike on one side of the coin. It looks like sort of like a mis-aligned die strike also. Can you show a reverse photo?
Thanks for the photo. Full strike. Close AM. A tilted die can also come into contact with the collar die which can wear the edge of the hammer die off to the point that it shows no edge/lip to the field.