In your article on the telescopes, you mentioned some of the work done refurbishing them in the late seventies. Could you have a look at this pic and tell me if the outer covering is the "Rexine" you refered to, and also, have the tubes been re-finished?
One train of thought is the tubes must be original as the engraving would not have been gone over again to remove the black from them.
TIA,
Brad.