Princess Cut

An old transitional cut diamond is set in a platinum millegrain setting in this vintage Masonic Shriner lapel pin
Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals
Princess cut is the name given to square-shaped brilliant cut diamonds.

The princess cut was invented in 1979 by Israel "Izzy" Itzkowitz.