These were made by 3 companies Schrade, Camilous, and Logan Smyth. All three were military contracts. The Schrade and Camilous versions are the best however the Logan Smyth version is appreciating the fastest due to there being so cheaply made that it is more difficult to find one in good condition. Supplyand demand. These were used by the airforce, navy and just about any one who had a survival kit. They were packed in new flight jackets, medical and survival kits and were all over the place. Many were snared and have ended up on the collectors market. I would like to suggest my book the collectors guide to switchblade knives. Published by Paladin press and available through Knifeworld, Amazon or any fine book store. ( Or personaized through me. ) It has the entire history of this particular knife with examples of all three ( from my personal collection.) If you have any further questions regarding them please feel free to email me. LT