The NASDAQ which didn’t exist before 1971 and initially was just an automated quotation system with no trading.

You are correct.
I worked at Bunker Ramo in Bridegeport, CT. from 1973 to 1977 as a computer programmer on the NASDAQ stock quotation system. IIRC, it had first gone online the year before. Made several visits to major brokers in New York City for tech support and setting up the quote terminals for individual brokers.
The NASDAQ system took in bid and ask quotes from brokers and computed and displayed the RBA (representative bid & ask) in real-time on the terminals.
The RBA bid was the median of all the bids.
The RBA ask was the median of the bids plus the median bid-ask spread.
The communication network was 9600 baud async modems.
The NASDAQ system ran on a Univac 1108, the code was assembly language.

One of the original features was to also display the commission that the broker would earn on a trade, when they had a client on the phone. We eventually removed that; the brokers laughed at us and said that they all could compute their commission in their heads.

When I left, the new network cutting edge was ARPA-NET. We were looking for a better way to connect the existing 4 network hubs than 9600 baud sync lines.