Those X's, are looking like freemason symbolism to me. Quick google and seems to be a long standing connection ... 1879 and further https://masonicperiodicals.org/periodicals/fcn/issues/fcn_19071879/page/11/articles/ar01101/
Disclaimer: I'm not a freemason. I was once invited, and declined. I do not know the password or secret handshake :-D
They seem to have even penetrated into my hotel! It's getting spooky :)