The RL16 in this exhibit is a twin barretter in a glass envelope with a B9A base. The RL16 Type designation was also used for the EC52 triode with a CV equivalent of CV1137 and this was on a B9G base - quite different and to avoid confusion w have added a hyphen to the Type designation.
Each of the barretters looks to be a single wire but close examination shows that each strand is made of a coil of very fine wire. Such a fine wire is not designed to pass a significant current so this is probably for HT regulation.
The GEC logo indicates that M-OV made this for the professional market.
The two separate circuits.
The thin glass tube envelope is 21 mm in diameter, and excluding the B9A base pins is 49 mm tall.