I recently acquired a PCGS slab to add to my set registry but when I try to add, it says bad certification number. Any thoughts on how to proceed. Thank you!!
Just contact PCGS. Usually it is a problem with their database.
You will need to send them front and back photos of your slab. That will help them determine the situation.
National Commemorative Medals of the U.S. Mint:https://www.pcgs.com/setregistry/u-s-coins/medals-tokens/national-commemorative-medals-united-states-mint-1940-present/alltimeset/195526