This is another firm favourite, the famous Amplidan, I've made a few of these keys in the past, this one will constructed slightly differently than the others as I now have a small Milling machine, here you can see I've milled out the base shape from a solid block of Acetal instead of using two separate pieces as previously, the original has a plastic moulding. It is sitting on a steel base plate, correct size but smaller gauge. It won't be an exact replica, Many of the parts on an original Amp are to comply with an isolated electrical requirement, for general Amateur use they are not really required so I will be redesigning the electrical side of things to make it simpler, but the original action components will be the same except for ball race bearings which most agree are better than the original pin pivot type. Below you can see the key almost completed,  On this key I've made the contact spring of heavy gauge brass and then ground off the thickness under the contact until I've got the "Feel" I'm after, this is some key, it makes my original Amp and my Blade feel positively resistive,  just requires the little weight under the knob and its finished at last.