Tachometer Type E-4 Weston 545 A-20 Havoc H-21 although they could be retrofitted

although they could be retrofitted to other models

but utilizes an electro-magnetic compensation system

A gallon of avgas is ~ 6lbs

made by US Gauge

Tachometer Type E-4 Weston 545 A-20 Havoc H-21 although they could be retrofittedHere is a WW2 vintage electrical Tachometer measuring up to 3500 RPM. This is the type used on the Douglas A 20 Havoc attack bomber (see photo of instrument location on the A 20 cockpit panel as illustrated in its flight manual) as well as the C 45 Expeditor transport (both aircraft used 2 each). The anchor symbol of the US Navy appears on the rear of the instrument, so it may have been used in an aircraft of the US Navy. Measures 3. 25 inches