I raised a similar question (copied below) back on 8/13/08. No estimates or actual numbers were forthcoming. Perhaps records are more accessible now?
8/13/08 Several messages have been posted recently about locating other OTs. Does anyone know (or want to make a guess - or still have access to the numbers) how many OTs there were during the period of NavFac operations? What percentage of the total does the Association now have as members or in memoriam?