There is virtually no information available anywhere about the MXR 01A that we can find. We have found an identical version of this reverb with ART badging, called the ART 01A. On some versions of this reverb a notification on the front panel that it is manufactured by “mfg by ART Applied Research & Technology Inc” others gave only a reference on the back. The official model number is the Model 191, which is generally only referenced on the back panel.
There is also an MXR 01 which is also virtually identical, but has the manufactured by ART written on the back panel. It also sold for significantly more than a Lexicon PCM 60 at the time! The MXR 01 was reviewed in May 1984 by Mu:zines, so we figured the MXR 01A would have been released the following year in 1985. If you have any information to share on this reverb, please contact us.