Practos extinction calculator
circa 1930
Milner extinction calculator
Heyde's Aktino-photometer
Degen Photo-metre normal exposure calculator
1900-1910
Heyde's Aktino-photometer
1905-1935
Eios aktinometer extinction meter
Zeiss Ikon diaphot meter. Watch pattern extinction meter in case
circa 1925
Drem Leica extinction calculator. Drem Zentrale
circa 1930
Ica Diaphot extinction calculator
Practos Exposure Extinction Meter and Case.
Heyde's Aktinometer. Extinction meter for use on camera ground glass screen
circa 1914