Mystery Coat-of Arms

For numerous years, I've passed by this unusual blazon that stands embedded to the walls of the famous Galatasaray high school in Taksim.

Placed on a wall that was later partially demolished to make way for the school's side gate, this unusual symbol defies all attempts to decipher its secrets. Who made it? What is its purpose? How old is it? It might be a symbol from one of Istanbul's old Levantine families or the remnant of a bygone Peran church, but none of these examples are backed by any kind of evidence.

Perhaps the most fantastic, but eerily plausible theory of its origins hints to the followers of Sabbatai Sevi, who referred to their messiah as "the King." But why such secretive people would construct such a visible mark for their idol remains a mystery, and in any case no evidence supports this hypothesis either.

A detail of the intricate reliefs surrounding the mystifying blazon.

Here is what we do know: The Galatasaray High School was founded in the late 15th century as an Ottoman "university", but its current incarnation goes back to the 1830s, when it was re-constituted as a Westernized college. This school has massive doors that were once used for its main entrance, but since the 1950s these stand locked and a side entrance is used instead. It is this add-on side entrance that has changed the wall this blazon is on into this ramp.

Do YOU know what on earth this sign is, or what it means? I'd like to find out before a random act of gentrification destroys this mystery too.