via this auction
"It is estimated that only around 200 of these were ever made. This one is serial number 21. Everything is working 100% and it has recently had a full service by James at Synth Repair Services, who also installed a couple of mods (details below).These synths are often favorably compared to the mighty MiniMoog. I can't offer a direct comparison as I have never played a MiniMoog, but I can tell you sounds enormous. I guess if you are looking at this auction then you already know this.
So, this auction includes just the synth itself and a power cable. There was never a printed manual for these (that I know of) but you can find a PDF online.
Information on the mods:
Oscillators 2 & 3 now have additional "low frequency" modes. Oscillator two now has Xmod to VCF (low freq) and Mod VCO 1+3 (low freq). Oscillator 3 has X mod to VCF ( Low Freq) and Mod to VCO 1 + 2 (low Freq). These are accessed through the Route knobs to the right of the oscillators main pitch control by turning the routing selector to the far right, where the extra modes are. This means that the mod is totally invisible and in no way changes the functionality of the M3X. They are just extra modes which can be accessed when needed. Low Frequency means that the oscillators can be pitched down further than normal in order to act as LFOs. They work very well, although if you pitch them down too far thay can affect the pitch of the other oscillators - a minor quirk that doesn't really affect anything as long as you know about it.
Overall, this is a stunning synth in stunning condition, with a couple of very nicely installed modifications which in no way harm the synth but add features which were not before possible."
