The No. 40 U. S. Navy Jack Knife is an old pattern dating back to before world War I. My particular knife is a 4 line Camillus knife dating to around the time of World War II. I suspect from the lanyard and and the modified pen blade that the knife was originally owned by someone who kniew how to splice lines and had access to a machine shop. The knife was issued and also sold in shop stores as the U. S. Navy Utility knife. It is essentially and e-z out jack knife. Thee-z out or easy out refers to cut out section of the knife handle which makes it easy to grab and open the main blade of the knife
The original owner modified the pen blades by grinding it into a coping blade. Coping blades are a popular choice for whittlers and scrimshaw artists as the tip is terrific for etching and doing fine carving work. The original pen blade may have gotten damaged and then modified or it might have purposely been modified for such work. One will never know. What I can tell is the knife was otherwise well mainteined and cared for.
Pattern: no. 40
The secondary blade was originally a pen blade. The original owner modified it by clipping the end and making it a coping blade, a common blade used in whittling and scrimshaw work.