W tube fitting.

Underneath the previously pictured NOS W tube was this fitting, at the time, I didn't realise it was a W tube fitting, until I dragged it out and opened it up. It revealed a second W tube, albeit gassed devastatingly. Looking closer, the lamp cap has come loose, and it looks to have taken the glass vacuum rod with it too, so I'm hopeful a repair can be made.
This is the first glimpse I have of the fitting, nothing given away here. Its also a recessed fitting, which would have given it a very clean look when installed.