JTO, thanks for the clarification. It was worth checking out as my recollection (from many many moons ago!) rather accords with your account. Times change though and there was a possibility that the c/s had a special significance for helios and/or Naval Ops. Seems not so, nothing to see here, move along please, we've all got homes to go to...
Once again apologies OP. Hope you got what you were after in spite of the severe drift.