I sat down with my new Vibroplex book and the actual unmarked key and compared point-by-point all the differences between it and the standard Vibroplex Original. I've decided that my earlier conclusion is just flat wrong — the key is most likely NOT an “Improved Vibroplex.”
I believe it is probably one of the other early imitations that Vibroplex sued for patent infringement. I don't have any proof, but you there are both striking similarities and differences between my key and a real Vibroplex.
There are some things that match the “Improved Vibroplex”, but not all of them.
For example, the damper on mine has is similar but not identical to the Vibroplex. The ATOZ and Vibroplex dampers were identical; mine is different from both of them.
The base of my key looks like like a ATOZ in shape; however the pinstriping does not match the ATOZ, and neither does it match the placement of the damper on the base. On the ATOZ keys I've seen, the damper is at the edge of the base. On mine, it more closely follows the placement of the Vibroplex damper.
The damper on my key also is slightly smaller, and is held with just one screw (although there are two screw holes in the base).
The circuit closer is a bit unusual, but it may have been something changed after production. the original paddle was replaced with one made of wood (elipitical in shape like a post WWII Vibroplex thumb piece), and the finger button appears to have been cut down in height. The circuit closer has a knurled knob as a nut on top of the based holding the spring tension; the head of the screw (usually on top of the Vibroplex base) is on the bottom side of the base on my key. The base is threaded on my key too, so the screw actually tightens into the base from underneath. A round metal (appears to be chrome plated) threaded disk screws down on the circuit closer screw from above, and serves as a base for the circuit closer spring. The knurled screw adjusts the tensioin on the circuit closer, though I don't know why that adjustment would need to be changed. It's a very un-Vibroplex arrangement.
The knurled knob is similar to those used on the wire terminals. It is big enough to rub against the finger piece, and the piece on my key has chips out of it from years of rubbing against the circuit closer knurled knob. The knob makes it rather close quarters for your fingers too.
Last night I attempted to re-assemble the circuit closer to standard Vibroplex configuration, but I didn't complete the job. It's apparent this arrangement was designed to function the way it does. There's an advantage of having the key base threaded for the circuit closer — you don't have to worry the movement of the closer will “unscrew” the screw out of the nut underneath the bottom of the base (not that I've had that happen).
So for now, I've got a key that is “the same but different” from my other Vibroplex bugs. I considered cleaning it up and replacing the paddle, but heck, that's what makes it so unique. I likely will disassemble it and clean it.
Part of me feels a bit guilty cleaning the crud from these keys I buy. After all, some collectors say the value is damaged by removing the “original patina” of the key. I see their point, but you know, I buy these keys for me, and think a good looking key is a much better part of a collection than a rusting, dirty one.
Of course, none of my keys are particularly rare. I have a few interesting ones, like a World War II Deluxe Original with the base painted Battleship Grey instead of chrome due to the war. I just enjoy these bugs, period!
I'm going out to the barn to try to cut some paddles for my Vibroplex bugs and my J-36s. Wish me luck!
73!