Comet (CMT) cryptocurrency is formally accounted on the number of ratings.. However, there is no up-to-date official information about its current status. Therefore, we can conclude that the coin is currently inactive.
DigiByte (DGB) is an open-source cryptocurrency launched in 2014. As of now, the coin is close to the bottom of the top 50 cryptocurrencies by market cap. DigiByte relies on the Proof-of-Work consensus mechanism hence it can be mined. The currency is deflationary and built using the Bitcoin code but unlike Bitcoin, its total supply is limited to 21 billion DGB. Another priority of DigiByte currency is the speed of transactions. Currently, the network is capable of performing over one thousand transactions per second.
CRYPTO20 (C20) is an “autonomous token-as-a-fund” and represents an Ethereum-based token. As of now, it is trading on a few exchanges with HitBTC being the most active exchange platform on its list. CRYPTO20 are so-called close-ended tokens. It means that no new tokens can be created. CRYPTO20 can only be purchased.