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OTCBTC is one of the largest Asian OTC (over-the-counter) cryptocurrency platforms. It also maintains the Exchange Market. 
Poloniex launched in 2014. It is based in the United States. It was recently acquired by Circle, a large Goldman-Sachs backed company. The exchange faced a hacker attack soon after opening which caused a higher level of security provided later. It requires a user’s physical address, postal address, date of birth, id, and phone number.
CoinZest exchange was founded in South Korea in 2018, maintaining deposit and withdrawal of fiat currency, Korean Won. At the point, the company’s website is down and Twitter media has not been updated since October, 2019.