Early Telegraph Key Ergonomics

I came across this photo serendipitously, while doing some follow up research for the book Susan and I are finishing. The photo is hosted on the Smithsonian Web site and the caption reads:

This 1844 telegraph key by Alfred Vail, improving on Morse’s original design, is believed to be from the first Baltimore-Washington telegraph line.

What strikes me about the design is that it has some ergonomic features built in.  The left hand screw controls how far off the desk the key sits and the right hand screw controls the amount of travel the operator wants.  Pretty nifty!