i don't know what it is...but my first thought was early japanese PLC ?
e careful before powering down.
try to see if there is any back up media onsite (probably cassette tape or 5 1/4" floppy from that era i'm guessing, even if you do find this its unlikely you can recover unless the interfaces are also there)
possible problems to be aware of
- if its always powered then the backup battery for program may be low and you could possibly lose the program
- older equipment power supplies can fail once powered down and then powered up, the inrush current can sometimes cause them to fail ( i have had this manyb times over my 40+ years) mainly with older VSD's and Switchmode power supplies
- the same as above for CPU and I/O cards