Saw this on Twitter:
https://famicom.booth.pm/items/2027812
This is a book by Orochi (famicoms.net (https://famicoms.net/), @oroti_famicom (https://twitter.com/oroti_famicom) on Twitter) that catalogs a bunch of the shop labels that were placed on the backs of Famicom carts. I don't know much about it, but it's awesome that someone took the time to document it.
Wish I could get a copy...
I've been following his blog for years, its a really good source of information about Famicom news in Japan.
He's written a lot of posts about his fascination with the second hand shop labels on carts, its really interesting.
A few months back he went through a warehouse stash of 26,000 Famicom carts and wrote a couple of really interesting posts about what he found out (not just about back labels, but other random stuff that only someone who had gone through 26,000 Famicom carts could discover):
https://famicoms.net/blog-entry-3688.html
https://famicoms.net/blog-entry-3693.html