Been waiting for this for some time ! Well done posting this.
This existence of this rating system is not well know even amongst elders.
I was "privileged' to take part in 4 of these ratings sessions with the CO over the years - it took about 4 hours+
Every elder in a circuit is discussed and scrutinised as to his eligibility to give talks / take part on RC program parts etc etc
Thereafter your are given a rating D / C / B / B+ / A
In all of the sessions I was involved in only 1 person ever had an A rating and that was the late Jim Hamilton who was a former CO in the UK if I am correct.