I have this 1957 D Lincoln in good shape that has the 9 filled in. At first I thought something on coin but nope with microscope you can see the cud filled. I thought it was pretty neat
Fun find. It is a die chip as cuds involve the rim of the coin. Read about it here. https://cuds-on-coins.com/cuds/ https://www.error-ref.com/cuds/