US Air Force WW2 Emergency Signalling Mirror (ESM/1)

Emergency Signalling Mirror Type ESM/1', complete with rectangular brown paper box with above inscription printed in black on front,, the mirror itself is rectangular-shaped with rounded corners, the reflective side bears a see-through cross in the centre and the reverse bears the same cross surrounded by a circular reflective panel, around this panel the rest of the surface is painted black and bears diagram and following inscription in red 'Emergency Signalling Mirror (ESM/1)