This is a used Chandler Germanium Compressor, with PSU-1.
The Chandler Germanium Compressor is a 1U rack-mounted Class A single-channel germanium-based compressor.
Until the Chandler Germanium Compressor came out, germanium transistors were considered to be a very desirable, but long-since vanished, relic of recording history. However, still capable of providing a unique contribution to the sonic process, Chandler Limited created a range of germanium-based designs, including the Chandler Germanium Compressor.
This particular Chandler Germanium Compressor is in excellent condition.