The XN-13 numicator from Hivac is a regular size tube. It features the gold-colored anode that is common to Hivac tubes. To my eyes, this seems to be a chromate conversion coating.
|Max current (guess)||3.5mA|
Here are some photographs of the tube from various angles, followed by a video of it in action. Some additional information is at the end.
Compatible tubes: GN-13A