I remember this mixer.  This mixer is a bit magical to me.  As a kid I would watch the analog needle dance as people talked and sang into a microphone connected to the unit.  I have an uncle who is a bass player and this was one of the mixers he used.  Here’s a little background on the mixer from Amazon:

SHURE M267 The Shure Model M267 is a microphone mixer-remote amplifier specifically designed for professional applications. The excellent performance, versatility and features of this complete, compact console make it an ideal choice for studio, remote, or sound reinforcement use, and as an add-on mixer for expanding existing facilities.

It is also ideally suited for use with audio and video tape recorders to provide multiple microphone inputs. Wide, flat frequency response and extremely low distortion up to +18 dBm output Extremely low noise and RF susceptibility Four switchable microphone- or line-level balanced-line inputs with individual gain controls and low-frequency rolloff switches.

MUMETAL shielding on input transformers Feedback-type input gain controls for maximum clipping levels and dynamic range Output switchable for line or microphone level Built-in switchable peak limiter cuts output overload distortion, adapts to power supply voltage LED indicator shows limiter operation or overload with limiter defeated Externally adjustable limiter threshold (-4 to +18 dBm) VU meter calibrated for +4 and +8 dBm with range switch.

Illuminated with ac operation Ac or built-in battery operation. Noiseless automatic switchover to battery in case of ac line failure. Battery test without program interruption Front-panel headphone level control and monitor jack drives almost any stereo or mono headphones; output can be additional unbalanced line feed to drive a tape recorder or power amplifier Direct mix bus for stacking units Automatic muting prevents speaker damage during turn-on and -off Low distortion, high-stability tone oscillator for line test and level checks.

shure m267 mixer

It was super cool when I picked up a working one.  Sadly, I’m not an audio engineer, but if you are, you can have it at a reasonable price.  Here’s a link to an auction I have running on eBay for it.