Hello Robbie.
I bought a new Ortec DRO system identical to yours from the man himself about fifteen years ago, he used to be a regular trader at engineering exhibitions here in the UK. Mine is also fitted to a Warco mill.
Dave isn't far off with the voltage, it originally came with an AC-DC transformer with a 6v DC - 600Ma output. This died recently, so I replaced it with another I had lying about which has a 6v DC - 300Ma output.
There does not seem to be anything quite like the straightforward Ortec display unit available anymore. I would like to fit a new DRO to my lathe, but I don't want or need one of the now common type of large complex display units with all the extra functions and keypad and whatnot.
Or am I just being a total arse!