In doing some book research on the AMEX hand signals, I was searching on the precursor of the exchange which was unofficially known as the Curb Exchange and came across this impressive 15 second video of how handsignals were used prior to the exchange moving indoors in 1921. Although I knew a bit of background on how the 'exchange' functioned it still surprised me to see people standing on ledges or leaning outside windows as in the clip while trading.