From what been posted after his post I'm guessing no one checked out the link posted by
@Mackaydon .
Here's from the link posted is what NGC says about the letters rating!!
"Grading Standards for Shipwreck Effect Designated Coins
SHIPWRECK EFFECT A — a coin exhibiting minimal surface disturbance from saltwater exposure, and exhibiting superior eye appeal for a shipwreck artifact.
SHIPWRECK EFFECT B — a coin showing evidence of light surface disturbance from immersion in saltwater, and may have some areas of moderate disturbance, not affecting central design elements. Coin possesses above-average eye appeal for shipwreck recovery coin.
SHIPWRECK EFFECT C — a coin displaying moderate disturbance to its surface from exposure to saltwater, while possessing at least average eye appeal for a recovery specimen. Accurate attribution and identification is not hindered by any surface impairment.
SHIPWRECK EFFECT D — a coin with moderate surface deterioration from saltwater exposure and with small areas of heavier disturbance, including corrosion confined to one side of the coin and/or its peripheries. Coin possesses at least average eye appeal for a shipwreck recovery artifact.
SHIPWRECK EFFECT E — a coin with heavy surface deterioration, but still possessing ample areas of moderate disturbance. Disturbance does not hinder assessment of its original condition and accurate attribution.
SHIPWRECK EFFECT — portions of the coin exhibit heavy to severe disturbance from saltwater exposure, with metal loss affecting the design. While accurate identification and attribution may be possible, it is no longer possible to draw conclusive determinations about the coin’s surface prior to saltwater exposure."
