Varieties of this type are not created by dirty stamping dies. The letters are incuse; the only way a piece of the letter can be missing is if a piece of hardened metal broke off the die. Every coin inlay after that time would have the same broken letter on it.

I'm not saying that makes the varieties with strange lettering scarcer... in fact it probably means they are more common, as cleaning the die doesn't fix the problem. Only a new die does that.

I still feel calling these "errors" in TCR is wrong. They are varieties and to be complete, TCR should list those known to exist. Need not have a premium value indicated unless it's known there are very few of a particular variety.