No idea Bob but there were plenty of them, 20-30ish?
This was 1970-72, and they had been there a few years judging by the marine growth on them. Maybe from Valiants or Canberras then?
Trials? Safety plus in the ability to drop 'em just about straight after take off into the oggin?
Trouble was the Sub-Aqua Club, and all the other clubs, had a rolling membership as folk were posted in and out, therefore it had no "corporate memory".