First Tom, i hadn't even seen your post when I posted that and second, I didn't say it was rare or even uncommon just not an everyday find when you consider the millions or tens, maybe hundreds of millions that were made.
Also, speaking from sad experience, lightly sanding staining over an etch seems harmless enough until it is now no longer visible.
What's third, Paul?
I know! I have a message for you. Should I send it PM or on the open forum?