I also remember watching the documentary on trading on floor of the stock market and amazed in the hand signs used there as well. It even has a name, Open Outcry, but this includes shouting as well.
The other one I'm reminded of is Tic-tac, the bookmakers' sign language that John McCririck helped to bring to popular attention on Channel 4 Racing in the UK.
I also remember watching the documentary on trading on floor of the stock market and amazed in the hand signs used there as well. It even has a name, Open Outcry, but this includes shouting as well.
https://en.wikipedia.org/wiki/Open_outcry