This is a Vault plugin version 1.6.1, and is missed on SpigotMC it was free before but somehow are disapeared from comunity i use it on server 1.12.2 and work perfect. I choice to deal with you here . This plugin belong i think to MilkBowl user. But here is a link for Vault https://www.spigotmc.org/resources/vault.41918/ that doesnt exist anymore.
This is a link for this official plugin:
https://github.com/MilkBowl/Vault
This is a link for this official plugin:
https://github.com/MilkBowl/Vault