Vibroplex invented the semi-automatic bug key in 1909.. It allows sending high speed code mechanically. One side has a pendulum to send dots, and the other side acts like a straight key to send dashes. They have a similar feel to an intricate pocketwatch, or perhaps a pinball machine. I got mine used from the estate of Ken Hartley, N2OHD, a silent key and the former manager of the Delaware Ham Radio Outlet. I made my first QSOs with it activating WM3PEN. RIP Ken.
Check out the Vibroplex Original Standard Semi-automatic Bug Key!