I designed and made this one in the early 1990s when I acquired a 2 pound slab of yellow brass. There is nothing special about this key except for its heavy duty construction. It is not patterened after any particular model - more like a key I would have manufactured if I was in the maritime telegraph business.The return spring is made of diamond-drawn music wire and fitted into a well where it would be fairly safe from loss during adjustment by an inexperienced radioman on the high and rolling seas. The brass trunions hold the 1/4 inch stainless steel adjustable pivot. The contacts are 1/2 inch diameter phosphor bronze and all four pieces of furniture are real bakelite. The insulation has been hi-pot tested to 2,500 volts and the current capability should be good for more than 100 amps, but we haven't proved that ... yet!