Bird 4410A Wattmeter, Thruline

The 4410A RF Wattmeter has the basic principles and “look and feel” of the Model 43 but transforms it into a highly accurate high dynamic range instrument. The mirrored-scale linear range meter has 2 switchable ranges, 0-1 and 0-3.
Power is read as a multiple of the value indicated by the pointer, the decimal point location depending upon the range switch position and the factor printed on the plug-in element. Power ranges covered by individual elements are 300 mW to 1 KW and 2 W to 10 KW, full scale. For most elements, accuracy is +/-5% anywhere above 20% of full scale. The circuitry operates from a standard 9V alkaline battery.

Features
Temperature-compensated accurate CW and FM power measurements from 200 kHz to 2.3 GHz and 300 mW to 10 kW
Uses special 4410-series wide-range elements
Wide-range accuracy over a 37 dB dynamic range
Quick Change (QC) connectors to minimize the need for adapters when making critical measurements