Some of the commentary here leads me to think not so much about the collector mentality and how much a collector is willing to pay for a particular key, but rather the intrinsic value of a particular key based on it’s merit.
So, what makes a “best” hand key? Certainly, it should look good but does it need to be “art”? What shape should the knob be? How high from the table should the knob be? What pivot bearings? What adjustment ranges? What about the mass of the “arm” ahead of and after the pivot bearings (balance)? Can we actually quantify the ideal hand key (show me the numbers!) or is it purely subjective?
Not pure subjective.
The spring must be adjustable and long, such that the force does in limit not change when you press the key.
All adjustments must by fine (screw thread) in order to make adjustments not good luck but precise and reproducible, independent of temperature and aging.
When you loosen a contra nut ( locking nut) and the screw can move sideways due to cheap thread, it is crap.
There must be standard a dust cover in order to prevent all what you can think about.
When you change keys and it turns out you can't reach your max straight key speed with the other one, don't use it
Contacts have to be wear resistant and reliable, shape is important, a sharp pinform will destroy the surface fast.
Construction of contacts has to be such that contact bounce on make and break is minimal.
There must be a way that you prevents to close the key completely with the contact spacing adjustment screw. (It needs clicking and a stop)
Hinges must be constructed such that the side movement can be adjusted to zero, but without wearing the hinges due to wrong form.
The knob may not cut your fingers apart after prolonged sending.
Key may not feel spongy.
There must be a current connection between the mass and the moving part of the key, hence not some current return through a hinge or a roller bearing.
In short: J38 fails on all these points, doesn't it? CRAP as said before.
The knob low or high is dependent on the mode of keying with arm on table (American way) or free in air (continental way). Figures has shown that carpal tunnel syndrome was less in continental way of keying.