What is relied upon in closed-book markets for finding the best bid/ask?

In closed-book markets, the role of brokers is crucial for locating the best bid and ask prices. In these markets, participants do not have visibility into order books, making it challenging to gauge market conditions directly. Brokers act as intermediaries who access various information sources and utilize their networks to gather intelligence on available bids and asks. They help facilitate transactions by providing their clients with the most competitive prices based on their knowledge of the market.

While market makers, pricing algorithms, and traders play important roles in different market structures, they do not operate in the same way in a closed-book context. Market makers may not have all the information needed to set prices accurately without visibility into the order flow, and pricing algorithms rely on open data streams to function effectively. Similarly, traders negotiating prices would struggle in the absence of visibility into the broader market or other participants' intentions. Hence, it is the brokers who are primarily relied upon to ascertain the best bid and ask prices in such environments.