Rare Kriegsmarine Carl Zeiss blc Binoculars Sight

Rare quick sight for use with various German wartime navy binoculars including the 10x80 80° Kriegsmarine binoculars and also used with early 12x60 flak rangefinder binoculars. Carl Zeiss maker coded 'blc'. Good used condition working order with the adjustable pointer arrow still fully operational.