Bird Electronic Corporation model 4275-100 Variable RF Signal Sampler.

According to Bird literature, the 4275 Series is a Variable RF Signal Sampler (adjustable Thruline® RF coupler) intended for signal observation, frequency counting, and RF monitoring applications. The 4275 operates over the 20-1000 MHz frequency range and provides an adjustable sample level approximately 35 to 80 dB below the mainline power.

This listing is for samplers with one type N(F) connector and one BNC(F) connector, the sample port is always BNC.  The manual for these units is located here: https://birdrf.com/hubfs/learning-center/manual-files/921-4273_75S.pdf

The last several photos show the performance of an attenuator with two of these samplers installed. The VNA sweep demonstrates the expected RF performance of the sampler over its operating range.

The adjustment mechanism operates normally and the locking lever functions as intended.

Marked:

Model 4275-100

Frequency Range 20-1000 MHz