Oxygen Flow Indicator, MK III, British Royal Air Force, 1942 A-26 They were essentially timers for

They were essentially timers for communications radios that broadcast a fourteen second carrier wave every minute

it is marked for the Inboard fuel tank

It is presumed to be a WWII-era indicator used in aircraft of the Japanese Navy judging from the anchor symbol on its face (lower left

using the scale along the outer perimeter

not surprisingly

Oxygen Flow Indicator, MK III, British Royal Air Force, 1942 A-26 They were essentially timers forHere is a WWII era artifact: an Oxygen Flow Indicator, Mk III, Stores Reference 6D 430. Multi crew RAF aircraft had these installed at crew stations, such as gun turrets, radio operator, navigator, etc., to indicate the gross flow (not the precise rate) of oxygen from the primary oxygen tanks (not portables) to the local junction at each station. Commonly used in aircraft such as the Lancaster, Wellington, Stirling, Mosquito, etc. The serial number on