Galen Leather card book
I've had this in my stash for a few weeks now and haven't gotten around to doing anything with it, until now.
It's no bigger than a credit card and is ideally suited to fit in a wallet or possibly a card slot in a Filofax or organiser. Like many other Galen Leather notebooks it's made by Tomoe River and is very thin but also high quality. I'm yet to find a pen to go with it but it's pretty unlikely I ever will! I will be keeping mine in my Filofax Malen Ochre Wallet as a back up notebook.