Ethereum Classic is the original protocol of Ethereum. As a result of the massive hack on the Ethereum-based DAO, in which around 14% of all ETH in circulation were stolen, a hard fork was proposed to return the stolen funds to their owners. This caused an ideological split revolving around the question of changing previous transactions in the blockchain. Some Ethereum holders rejected the hard fork, and decided to keep using the original protocol, based on the principle that the blockchain is immutable, and cannot be changed.

ZCoin is a privacy focused cryptocurrency built on Ethereum. The ZCoin protocol enables anonymous transactions with cryptography that utilizes Zero-Knowledge Proofs (ZKP). ZCoin increases privacy on their network by using a coin-mixer contract that wraps transactions in a serial number and destroying wrapped coins once they have been redeemed.
Zcoin was the first cryptocurrency to use a Merkle Tree Proof (MTP) as its proof of work algorithm. Merkle Tree Proofs are an innovative solution to achieving network consensus, and can increase transaction time while reducing the centralizing tendency of ASIC mining.

Gulden is a Dutch cryptocurrency based on a native blockchain with a Proof-of-Work (PoW) consensus mechanism. Gulden has gained traction in the Netherlands, where it can be used to make P2P payments, as well as send funds to an IBAN account. Gulden's marketing efforts emphasize the network's security and faster transaction times. Gulden's PoW² consensus combines aspects of PoS with PoW, and allows witnesses to add transactions to blocks after they have been mined. The network is powered by the NLG coin.