[Tcards-Please]

I just saw a recent post with a 1915 Joe Jackson card that had the "Surface Ink Added" label which brought to mind this question. I have never fully understood why some cards get a numerical grade with noticeable ink/pencil marks on the card and others get the "A" "Surface Ink Added" label?

I can certainly understand if someone is trying to be deceptive in trying to match color ink to make the card appear as original and unaltered. But when it is blatant and clearly can be seen as ink/pencil, why the "A"?

I'm sure there is some logical explanation.

Here are two with pencil. The Wilhelm has it on the border and "B", and the Shean, well I'm sure you can find it.