Patent ID: 7890417

Claim:
An electronic trading system for anonymously trading at least large block trades of securities, comprising: a plurality of system user interfaces for system users to communicate with an electronic trading platform for anonymously trading at least large block trades of securities in buy and sell transactions; a communications network for bi-directional communications between the plurality of system user interfaces and the electronic trading platform; and the electronic trading platform in bi-directional communications with the plurality of system user interfaces through the communications network, with the electronic trading platform at least comprising, first means for receiving and comparing firm orders to buy or sell specified securities from system users and auto-matching such firm orders to buy or sell specified securities between counterparty system users to automatically complete a transaction; second means for determining if trade pricing for auto-matching firm orders to buy or sell specified securities between counterparty system users is according to pricing rules, with such pricing rules specifying that trade pricing will have a predetermined relationship to a national best bid or offer (NBBO) price spread that includes auto-matching firm orders if the buy and sell prices for the security are within the NBBO, the buy and sell prices for the security are outside the upper limit of the NBBO, or the buy and sell prices for the security are outside the lower limit of the NBBO; third means for determining if the NBBO price spread is a valid NBBO price spread; and fourth means for commencing and controlling a negotiation between counterparty system users that have firm orders to buy and sell specified securities on the electronic trading platform that have been considered for auto-matching at the first means but could not be auto-matched because trade pricing was outside the pricing rules or the NBBO price spread was invalid.