BOSS Taiwan PQ-4 in very good + condition - March 1991 production.
100% original circuit  & in perfect working order. 

from bossarea.com

Boss PQ-4 Parametric Equalizer

THE PQ-4 has over time become quite rare. It was never a big seller and as Boss presently doesn’t make any parametric equalizers, they are highly sought after. You can adjust Presence, Low Level boost or cut, Mid Frequency range between 100Hz and 1.6 KHZ , and a High Frequency range between 500HZ and 8KHZ. Each frequency range selector has it’s own individual levels for boosting or cutting specific frequencies, plus it has a -18 to +18 over all level boost or cut.

Specifications

Controls: Presence/Low, Middle, High, Level
Connectors: Input, Output, AC Adaptor
Current Draw: 23mA
Weight: 410g
Input Impedance: 1 M ohm
Output Impedance: 1 k ohm
Residual Noise Level: less than -98dBm (IHF-A)
Recommended Load Impedance: More than 10kOhm
Recommended AC Adaptor: PSA Series