A few nice business card size images I found:
VIA EPIA-P900 Pico-ITX Board - Card
Image by viagallery.com
This is an image of the VIA EPIA-P900 Pico-ITX board shown with a business card for size comparison.
kevin's wallet, side view
Image by ksbuehler
to access the inner cards, they can simply be slid out and slid back in, no need to squeeze the clip; add/remove business cards to adjust the tension
