Rotameter, Anti-Icing Fluid Flow Indicator, Fischer & Porter Type NW, DC-3

This is a Rotameter anti-icing fluid flow indicator for a dual engine propeller anti-icing system.  The instrument was used to titrate the flow of anti-icing fluid from the fluid reservoir to the propeller slinger rings, by adjusting the two needle valves to the required flow rate, up to 8 quarts per hour.  The flow tubes are pyrex glass.  The instrument was lighted and a bulb receptacle is located in the upper rear of the instrument.  

This Rotameter, Type NW, appears to be made from the late 1930's to early 1940's.  Its manufacturer, Fischer and Porter, began business in process instrumentation in 1937.  The item's sales literature pictured in the photo gallery is from 1940, and show a DC-2 or DC-3 on its cover. The brand name "Rotameter" appears in raised letters vertically down the face of the instrument.  The instrument has a metal bracket (see separate photo with it attached), assumed to be for installation within an aircraft.

Measures 3.25 inches diameter, 4 in square with bracket, and ~3 inches deep including ports.  The needle valves rotate stiffly, the floating indicators are stuck in position at the bottom, and some white particulate residue is in the pyrex tubes.