X17-Mind-Papers - die Wiederentdeckung der Karteikarte<br /> https://www.youtube.com/watch?v=wxZMia35usc

Mind Papers has a variety of small leather covers (folders) with binder clips for storing one's note cards. They range from smaller than A7 up to A5 sizes.

They're broadly reminiscent of smaller versions of the Everbook, though I suspect these came first given the 2014 post date.

https://everbookforever.com/

Everbook appears to be a variation on some of the GTD, PKM, and productivity traditions done on larger loose slips of paper (instead of notebook style) with an incredibly lovely leather folder. There's a lot to like here for those stuck between love of slips and notebooks. Its reminiscent of project planning and to do methods using ring binders or FiloFaxes.