I'm neither a completionist nor a speculator. Interesting designs and defects appeal to me, so I tend to open most of my decks when I get them. I'm also a sucker for a good grab bag sale.
A buddy mailed me some casino-used decks he found in a thrift store. Their tucks are torn, and their edges are clipped, but I think these may be some of the most expensive decks I have. Someone lost a lot of money over them, anyway
