Embossing
 

Ive noticed in the BST that there have been several T206 Cards for sale that have been embossed to the upper left corner. One of these cards was a Cobb, red, last week I believe. Anyway, they seem to all have the same embossing. Does anyone know why? Was this a singular owner at some point years ago, or was this particular "logo/Letters" common for some reason then? Sorry if this has already been asked, couldn't find anything on it.

I don't know the ones you are speaking of particularly but it is not uncommon to find same owner characteristics on cards. Many have a certain type of writing or stamp.