There are a few certificates listed on the Heritage Auctions archive. Surprisingly, the priciest piece there is a 1950 issue, which sold for $3,107 in 2014. It's beautiful and has nice football graphics and content. Going back, there are a couple from 1919, issued by the Indian Packing Company. Those pre-date the GB Packers, though apparently, the team grew out of that entity. Those certificates each sold for less than $700. And they also have a couple 1924 Acme Packers certificates that sold for less than $600. Everything I described sold since 2011. The Indian and Acme pieces aren't especially eye catching, though they are interesting documents. I think you'd have to buy and sell it as a piece of art. I don't know if it has any tradeable value on any exchange, or any transferable ownership rights. It's just a piece of interesting paper.