A US military aircrew survival knife usually blaze orange in color that has a single side opening switch-activated blade propelled by means of a bar spring. Opposite this is a hook sharpened to cut the shroud lines of a parachute (looks somewhat like a large popcketknife can opener). Sometimes the automatic function is reversed to the hook to comply with local laws regarding switch blade knives or user prefernce. Was made in quantity by Schrade/Walden, Camilus and others from the 1950's to the early 1990's.
Handle is synthetic stag. An updated model, with a stronger coil spring less prone to fatigue and able to be easily disasembled with a hex wrench has superceded the earlier rivited design although the former is still commonly available. It resembles a large conventional pocket knife.
Although e-bay does not permit the sale of switch blade knives, a search for mc-1 will reveal the futility of such a rule.