The Marshall JMP-1 is a rack-mounted guitar preamp that was first introduced in the 1990s. It's part of Marshall's "JMP" series, which stands for "Jim Marshall Products,".  The JMP-1 preamp was designed to emulate the classic Marshall tube amplifier sound in a convenient rack-mounted format.

It has 2 overdrive modes, 2 clean modes, bass shift and 7 editor switches that can be controlled with the data knob.  You can also make your own presets and store them in the patch settings, which I believe can store up to 99 presets.

I've tested this to the best of my abilities and have found it to be in very good working condition.  All knobs and buttons work and the output was clear without popping or other noticeable anomalies.  There's some slight noise when turning the output knob.

The MIDI features are untested.

The Marshall JMP-1 includes a power cord.  It appears to have had the original tubes replaced.