The good ole J-37 key served with the U.S. military during WWII, the Korean War, and through-out the Vietnam era. The J-37 key was the real workhorse during those years and carried the bulk of the action. The J-37 key has been built into many numerous and different configurations with the addition of different bases. One of these different styles is the J-45 in the picture below. Where does the J-37 name come from? Well, it was the U. S. Signal Corps that assigned their telegraph keys with the letter "J" and then a number. This practice started during the WWI era and ended in the 1950's. The number range begins at J-1 and ends at J-51.
The J-37 CW key featured on this page has some markings molded into it. Just to the left of the arm is "J-37" and to the right of the arm is "JFC". The JFC marking indicates that the key was made by the company "JFC. Elex INC". I have been told that they made this CW key from 1915 until the WWII era. The key is shown above removed from the leg strap.
The J-37 key in any of its configurations is a fun key to use. It is lightweight, portable and simply stated, as tough as nails. The J-37 key incorporates a leaf spring design that many folks find a pleasure to operate. Some believe that this leaf spring design gives the operator a smoother feel of the key over that of a coil spring design such as the J-38 key. The mechanical characteristics of the leaf spring, to some CW aficionados can not compare to those of the coiled spring design, even when modern keys such as a recently manufactured Nye Viking Speed-X CW key is used. I do wonder though, how well the leaf spring design would hold up to either a repulsion or attraction magnetic designed CW key in their eyes. It certainly would make for a fun and interesting conversation on the air.