There is no doubt that the Marconi PS213 type keys are very fine keys indeed, not overly complex but it is obvious that great care and thought went in to getting a very fine action, I have previously made a fairly close copy of one of these keys (key130) and now made another but a G3YUH version, I have made subtle changes to the original design,  the base is thicker the main key body longer the width of the bearing block narrower a more rounded knob and quality Ballrace bearings, all of  which give a more snappy heavier feel, which is very pleasant to use, an excellent key!!