#3 - another great example of a knurled brass thumb-screw in use on another 
type of "clockwork" device (other than a clock) ... note the adjusting knob 
at the base of the sound-horn on the linkage that couples the audio 
vibrations to the needle that cut the grooves into the wax cylinder ... this 
is one of Edison's early production model phonographs (this one dates about 
1899):

http://upload.wikimedia.org/wikipedia/commons/a/a0/EdisonPhonograph.jpg

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"There is also an artificial aristocracy founded on wealth and birth, 
without either virtue or talents ... The artificial aristocracy is a 
mischievous ingredient in government, and provisions should be made to 
prevent its ascendancy."

>> Bob is spot-on about #3 ... these knurled thumb-nuts are quite common,