I have a vintage BC slim stamp too!
I do it all - labels, stamps, handwritten...
just the site URL, "visit this book's online journal", and "BCID:", and are small enough to use even on crowded title-pages. (I mainly use mine to stamp the book's *last* page, or the first page of the index for non-fiction, as a reminder to the reader to journal the book if they didn't do it before they read it. I hand-write the BCID beneath the stamp.)
I know this is an old thread, but way back when I first discovered BookCrossing, I made a custom stamp to assist with my BookCrossing. It says:
Register your find @
I also have a bookplate that I put in the front of the book, and a custom label that says "Not for sale. Never for sale. Just for you."
I just can't afford to buy só many labels for all the books I release.
I cut out the labels with a scalloped-edge scissors before affixing them to books. In this way, I can Identify MY books by sight alone. :D
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