This exhibit is the Welsh Peanut Tube Type WT501. It features an external grid and the base was also supplied by Welsh.
The original box.
Thanks to Joe Gruber for sending the images.
The thin glass tube envelope is 16 mm in diameter and, including the peanut base pins, is 50 mm tall.
Reference: Joe Gruber.
Updated November 26, 2020. shape:thin.glass.tube construction:pinch type:triode age:pre.1920 base:peanut pins:4 pin: