The wheel?
The internet did exist 20 years ago and was useful for trading, costs were more prohibitive but plenty of people traded using the internet in 1997. I believe satellite net was a thing already back then, so you could trade from anywhere, theoretically.
I had already realtime datafeed in the early nineties from :
- dow jones teletrac by some "twisting of cables for phones"
- signal by satellite
Teletrac could only be rented at $1,850 a month plus 19% taxes.