This is the official Grand Master flag of Sovereign Military and Hospitaller Order of Saint John of Jerusalem, Rhodes and Malta.
Insignia of SMOM The Sovereign Military Hospitaller Order of St. John of Jerusalem of Rhodes and of Malta, better known as the Sovereign Military Order of Malta or SMOM, is a Catholic lay order that claims to be a sovereign entity and has permanent observer status at the United Nations. SMOM is considered to be the most direct successor to the medieval Knights Hospitaller, also known as the Knights of Malta, and today operates as a largely charitable and ceremonial organization.
It also symbolises the maltese cross ( George Cross ) that is in our flag.
About the shell: It is a multi break shell to us maltese knows as " Kulur ta' Tlett fethiet u Bomba " and symbolises the Grand Master flag.