16013 Serial Number Damage

[bthsjava]

Hi All, I bought a 16013 via Ebay which passed their authenticity guarantee. The watch is beautiful and everything looks good. Clasp Date Code is J4 which matches the white Buckley Dial. The one thing I noticed on Ebay's inspection is that it said "Worn Off" serial #. I opened it up and noticed that it seems that the serial # was either "Stabbed at" or corroded?

I don't think it looks intentional as I feel there would be better ways to do this if someone was trying to hide the numbers but has anyone seen anything like this before or can give some information on why this may have happened?

Don't think it will effect performance but I guess it will effect the future resale value.