The DE55 is a general purpose triode from Cosmos. The maker is Metropolitan Vickers (Metrovick). The original data-sheet was included in the box.
The cylindrical anode is mounted vertically. Note the glass bead holding the filament tension spring.
The complete assembly with the helical grid extending beyond the anode. The grid winding is secured to the single support rod by the notch and peen method as can be seen on the left of the image.
The helical grid.
The filament tension spring held in the glass bead that is also connected to the anode support.
Here the spring can be seen to hold the top loop of the filament.
The balloon envelope is 50 mm in diameter, and excluding the B4 base pins is 94 mm tall.
References: Data-sheet, Data & 1043. Type DE55 was first introduced in 1926. See also1926 adverts.
