Zerify Inc (ZRFY)

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Once the market maker has entered a price, he or she is obligated to either buy or sell at least 1,000 securities at that advertised price. Once the market maker has either bought or sold these shares, he or she may then "leave the market" and enter a new bid or ask price to make a profit on the previous trade.


http://www.investopedia.com/university/electronictrading/trading3.asp