According to the OTC Markets Group, their recently launched Expert Market "is a private market to serve broker-dealer pricing and best execution needs in securities that are restricted from public quoting or trading. Restrictions can be based on issuer requirements, security attributes, investor accreditation and/or suitability risks. Prior to this, market makers could only exchange quotes verbally between themselves and licensed brokerage firms. Adding this new function allows broker-dealers to exclusively see one another's bid/ask/size quotes in a quotation system hidden from public view.