Dual-Action Hidden Blade

Hidden blade prop from Assassin's Creed games. This has a dual-action switchblade mechanism that allows it to extend and retract triggered by a ring on the user's finger.

At least in theory. I was never able to tune the mechanism so that it would both extend and reliably retract. I'm giving it up for now, but the design is free to modify in case someone else is able to perfect it.

http://youtu.be/Yv1VngScMQY
https://youtu.be/4eiZ8Y5Iq5w
https://youtu.be/frmb1_U9R1Q