"The Marshall Time Modulator is a classic analogue delay and modulation unit from the mid-'70s. Designed by the late Stephen St. Croix (aka Stephen Marshall), it became popular for its ability to produce deep flanging and crazy modulations."
"The 70's was full of creativity and new ideas. This Time Modulator was a direct product of that era. It can do high quality time related effects like positive flanging, negative flanging, cardboard tube echo, automatic double (and triple) tracking with pitch and delay dithering, resonant flange, straight vibrato, 'circus vibrato', arpeggio, pitch quantizing, high Q filtering, drum tuning, echo, Leslie, doppler panning, etc. "
Here's a link to Studio Electronics website where you can learn more about the unit and it's creator Stephen St. Croix. They are authorised to sell and repair the Time Modulators. http://www.studioelectronics.biz/Services-Marshall-13.html
Here's a link to a current Ebay auction of a Marshall Time Modulator.
and there is also a plugin version of this effects box made by Mr. St. Croix's
company Intelligent Devices http://intdevices.com/proaudio/product/show/11/