Mr. Midnight
A cud, as I understand it, is caused, by a pit in the die. part of the metal of the surface of the die has corroded or chipped.
There could be a population of coins with the identical cud, produced before the die failed altogether…
Do I have that right?
That's absolutely right. I my opinion, several cuds on the same coin in the same place and year, should be able to be “elevated” to the term variant?
A couple of examples from Denmark, where they are accepted as variants.


In the numista catalog, there is a Belgian coin, a 5 francs, 1986, km163, which has been accepted as a variant by numista
N#757
Here is what I can show of it:
Globetrotter
Coin varieties in French:
https://monnaiesetvarietes.numista.com