This looks like a "wrinkle" in the coin It is raised up. It is not a scratch, gouge, dent, etc. It is probably too light to be a crack, I think, sooo.... ??? It's hard to photograph, but is very clear to the naked eye in-hand. It runs from the top of the "f" to the top of the "d", along the top of the "d", and then connects to the edge of the "o". It is raised almost as high as the letters from the coin surface, and has the same luster as the rest of the surface. The lights here are unflattering to photos, sorry.
What you are seeing is a clash...here are a couple of other examples of clashed dies that are used for markers for the 50c 66 SMS DDO-025, stage B, and the 50c 70D DDO-003, stage C. Larry Nienaber
Thanks guys As a side note - carefully checking other coins of the same date/mint from that bag, I found 2 more identical clashed coins. 1971D. one is fainter than this one, one is stronger - I am guessing the clash marks were pounded out over time
