You have asked a good question here and it is hard to say for sure how the corrosion can eat away a coin without taking away the letters and date. I don't know how this works but I have seen coins eaten away by near half of their thickness and still the letters are there. I'm thinking that on corroded coins the corrosion attacts the weaker metal first and this may be what leaves the uneven patterns. coins are usually a alloy of different metals and the alloys sometimes don't get totally mixed together. on the obverse side of this coin there is what definately looks to be corrosion eaten areas so the reverse side may be also.
If there is any coin composition with the best chance to make a pattern as it corrodes, the CuNi alloy is it. Remember that CuNi is the only coin metal that Nic-a-date and such work on , as the crystallization pattern is different with the raised devices such as the date and lettering, than the fields which are more reactive to the chemical all due to difference in localized striking pressure. I think Rascal had the best answer, corrosion and possible burial.
Don't waste your money sending to ANACS, PCGS, etc...to be honest, one of the first things you need to do is think "what happened during the minting process that could have created what I am seeing?" As for me, I can't think of anything at the mint that could have caused your coin to appear as it does.
There are really only 2 possibilities. (1) could be explained by a process within the mint at the time of striking, or (2) Post mint damage. If one can't explain #1 , then it must be #2. Since every step in the minting process is documented, but every possible thing that can happen to a coin after leaving the mint could happen.
Does anyone know the value of a 1900 v nickel with a error stamped in the face of the coin. It's a v stamp
Post mint damage or counter stamped , there are collectors whom collect counter stamps. As for value I have no idea as I'm not into damaged coins,
Well it's been years since I have posted on this coin. I still have it in my possession. I have taken it to several dealers and they have no idea either. I've always been stumped on this one. Maybe someone new to the forum has the answer.