This is a used API 527 compressor, it's in mint condition.
The API 527 Compressor / Limiter is a single-channel 500-series VCA compressor taking its cues from the 225L console dynamic processor and 2500 mixbuss compressor. The API 527A includes both feed-forward and feedback topologies which are selectable via the New/Old switch. These modes offer a choice between an aggressive, punchy and “modern” sound or a more laid back vintage sound of more typical classic compressors. The 527A also boasts a Soft/Hard switch that changes the knee for a natural, transparent “over-easy” compression or the harder knee type for more aggressive curve suited for more severe limiting. The 527 A also includes API’s Thrust found in the original 2500 which applies a filter before the RMS detector circuit to minimise the impact of low-frequencies on the compressor and keep a punchy bottom end. At the heart of the compressor’s sound lies the 2510 and 2520 discrete op-amps that deliver the signature API punchy mid-forward sound. The output control works akin to the Ceiling control on the API 525 Compressor with the output level remaining fairly constant regardless of ratio and threshold controls.