The CT-6SSD is a gas filled or soft triode. The presence of the gas enables it to be the Super Sensitive Detector of the SSD in the Type designation but also limits the anode voltage. Unusual to find a soft valve being made in 1926.
The box anode is narrow front to back. The filament tension arm can be seen on the right.
The anode face view and the seal is on the right. The seal being a brand device.
Looking into the top of the anode reveals the wire grid and the CT on the anode. The grid connection enters the pinch through an extra glass tube. Ionised gas and a small space between the wires suggests the possibility of unwanted conduction.
The filament tension arm looks to have a filament attached but in fact the filament is missing.
The balloon envelope is 42 mm in diameter, and excluding the B4 base pins is 98 mm tall.
References: Data-sheet & 1043. Type CT-6SSD was first introduced in 1926. See also1926 adverts.