The model type is ACM (Alice Custom Modular). The quality was as good as you could get at the time…. probably as good as you can get now.
I did design those mixers so I can probably answer any questions even though it was a long time ago!
On the terminology, ES is Echo Send, FS is probably FB, foldback. I don’t have any circuit details or multiway pinouts for the desk, but I’m sure you will find that it is logical.
The metering is BBC spec PPMs and originally the desk would have been inspected and passed by the IBA for transmission use so the technical performance will be near perfect even after all this time.
Reading through your message again reminded me that one of the facilities we equipped was an OB truck for Stan Horobin, the chief Engineer at Solent…. It could be that one.
I would expect that it dates from 1976 to 1980….. we did the first installations in Glasgow and London in 1973 but these production mixers were a little later.
All I can say is ‘well done!’ This is an example of one of the best mixers made in the late 70s/early 80s.