Just an update on trademarks after some more digging.

The "Regina" and "ES in a circle" trademarks were registered by Edouard Schroeder in 1903 and 1905 respectively.

Charles Edouard and Max, 1921 to 1928 registered "SF", "SF in a circle", "S in a rhombus (square)", "ALBATROS" and "FOX" trademarks.

Pete