Just when I thought I'd seen it all, along comes this website: coincollectingboards.com. Yes, visit that site and you can learn that "One of the really fun features of old coin boards is that many have the names of the vendors who sold them rubber stamped on their backs. See how many names you know!"
Not only does this dealer specialize solely in what appears to be old press-in coin albums, he's written a book about them! And you thought your collection of Charles II pattern farthings was esoteric!
Apparently, "With 64 pages in full color, this book is a sheer delight and belongs on every collector's coffee table." And furthermore, "Fully understanding and appreciating vintage coin boards requires a lot of photos, both overall views and details. This book has everything you'll need to get a handle on the subject and become your own expert."
I have heard of people that collect fruit stickers (yes, there are websites about them as well), but the very existence of this site re-defines for me the sheer scope of things that people can collect!