1940s USAF B-1 Signal Mirror Front
This flash photo shows a 1940s 3"x5" glass USAF type B-1 Signal mirror (Specification 41063) from the front, together with it's paper envelope. See the next photo to see the other side of the mirror.
The United States developed the B-1 emergency signaling mirror (signal mirror) in late World War II, and production was started in 1945, but they did not reach the troops before the war ended. The B-1 used a ring of red retroreflective "ScotchLite(TM)" material around the sighting hold to create a red round virtual image of the sun focused at infinity as a "red dot" sight. The next generation of US military signal mirrors to be developed was the Mark 3 with the retroreflective mesh aimer, in 1949.
The French military, however, has stuck with the B-1 type of aimer, in their "Miroir de Signalisation SOS Type 643" and "Miroir de Signalisation SOS Type 644" signal mirrors.
There's a nice description of the design of the B-1 mirrors here: p. 21, column 1 in "Heliographic signaling mirrors", R.S. Hunter, NBS, in Air-Sea rescue bulletin, US Coast Guard, publisher, v3 March 1946, pg. 29. babel.hathitrust.org/cgi/pt?id=mdp.39015010566720;view=1u...
The patent description is here: www.google.com/patents/US2412616