Type G Pliotron with the UV four pin bayonet base was used by the Signal Corps in the USA and designated VT-11. It was first sold to the US Army in 1918 and found service during WWI. The slightly earlier version used by the US Navy was the CG-886 initially fitted with a three pin base with the pins arranged at the points of an equilateral triangle.
The anode is made of nickel and is a closed cylinder about 8 mm in diameter and 10 mm long.
From the Tyne Collection.
The original box.
The box end with Type VT-11 printed on it.
Thanks to Joe Gruber for sending the images.
The balloon envelope is mm in diameter and, excluding the UV base pins, is mm tall.
References: J Gruber, & 1047. Type VT-11 was first introduced in 1918.