1995-96 Topps Gallery Player Private Issue question
 

I have seen these with and without the stamped serial # on the back. Anyone have any insight or ideas on this? FWIW, the PPI seal is under the UV coating so I do not think the PPI seal is an alteration. I am thinking some went out the back door of the factory? Also, was part of the print run on these cards junked for lack of sales the way that the baseball issue was?