The orange knife is a MC-1 hook blade knife, funny story about it. A common rumour/mis-conception is that the manufacturer mis-read into the specs and made a switchblade with it, and that the hook part was supposed to be the switchblade portion, not true. The previous version had a fixed hook blade, no knife blade, and the handle was made of rubber. The knife is stored in G-suits (leather pocket) and on parachutes risers with the hook blade opened, allowing the aircrew member to use it quickly. The MC-1 knife is still used by the USAF today.
The hook blade is very sharp, when I first came into the USAF and the Aircrew Life Support career field, I was cleaning and oiling one of the knives as I wiped the hook blade down my finger went into the groove, dang near took my pinkie off.
Parachutes in the USAF and the Parachute harnesses have a PLD installed (Personnel Lowering Device, PCU-10/P is one type of this) to lower yourself to the ground from high tree canopies (Think Viet-Nam and a high jungle canopy). Opening the chest strap would cause you to tumble forward and out of your harness and take a head dive to the ground. The PLD is 150 feet long, last 25 feet has stripes to let you know you are near the end of the rope.
Mike
USAF Retired