Great post, and a fabulous overview that all beginners should read!!!
Unfortunately, I'm going to have to disagree with your choice of examples for cleaned coins. In my opinion, both the coins you showed have been cleaned/dipped. The second one was done long ago and the coin has since retoned.
Truth be told, most bust halves from this time have been cleaned in their lifetime, so it becomes a matter of what you can accept.
Here is an example of an original skin half dollar:
Here is an example of a bust half that has been cleaned, but has since retoned in an album:
Again, great post....Mike
