TBH, I had no Idea as to why it's called Solomon's knot. Actually, it's only one of its names...
Semper invicta? Not in that outfit!Grand Coat of Arms of Metropolitan city of Warszawa (= Warsaw, latine Varsovia)
Crown symbolises it was Royal Metropolitan City.
Mermaid is symbol of Warsaw (legend of mermaid who settled there)
Semper Invicta - always unconquered
below is cross of Valor - Virtutti Militari - to the military virtue