Hi Reprobus . Thanks for detailed post .
Certainly a lot different to mine . See http://www.mycncuk.com/threads/13959...TCL125+boxford Skim through and you will find pic of the guts of mine.
Doyou know its history ?
Certainly looks to be very much adapted from original Although original motor , choke and power supply transformer seem to be there . with a few added items of "bespoke" origin.
My motor drive was a Lenze type and looks at first glance to have been replaced by the gemini contraption on the right . More details of that would be useful.

Your BoB is a very old style compared to the sort we seem to see more often these days https://www.ebay.co.uk/itm/393334570...cAAOSw-7ZgpVSd
There may be some info on the underside regarding the functions of the terminals on the near end of your board . but depending on where they are connected this may give us some clues .
Just beware . I cant see any info to specify whether the Gemini controller is an "isolated " drive . If not there may be some high voltages waiting to bite you.