Well, we are talking about the RM57 and RM58 Compressors which, as you say, are essentially the same beast. The RM68 noise gate is mentioned because it has some similar circuitry and we are trying to find out the components used.
As has already been mentioned, Roger Mayer refuses to help in any way and I would not recommend contacting him as it is a very unrewarding experience!
The schematics available don't give any clues as to line-up, and some of the transistors are not identified.
So that is where we are right now.
Hopefully Dan can have a look at his unit and identify some of the parts.
Thanks for the RM57 pictures link - very helpful.
I notice that one of the 2N3820 FETs has a red mark painted on it which would seem to suggest it is a selected part. What the criteria is for that I don't know. It is the same FET as used on the noise gate and I remember some detail being given in the RM68 literature. That's why I was asking about it.
I think the release 'switch' was only used on the RM58. On the RM57 it was a 2M2 pot.
I didn't find the HELIOS driver circuit you described.
Can't say that I see the similarity with the Octavia circuit (?).
Thanks for your help.