Namecoin

Namecoin (Symbol: ℕ or NMC) is a cryptocurrency originally forked from bitcoin software. It is based on the code of bitcoin and uses the same proof-of-work algorithm. Like bitcoin, it is limited to 21 million coins.[4] Namecoin can store data within its own blockchain transaction database. The original proposal for Namecoin called for Namecoin to insert data into bitcoin's blockchain directly. Anticipating scaling difficulties with this approach, a shared proof-of-work (POW) system was proposed to secure new cryptocurrencies with different use cases. https://en.wikipedia.org/wiki/Namecoin