The DL35 is an octal based audio output beam tetrode for use with dry batteries. This is no miniature valve so the probability is that the broadcast receivers that it was to be used with were large static pieces of equipment.
Clearly once this was part of the BBC stock. The date looks like 51 or 57.
This second label that is stuck partly over the first has a date of 17/01/1941. This must be the label design date as the DL36 originated in 1946
The clear part of the glass. The filament springs can be seen as can the tops of the three grids.
The wide glass tube envelope is 30 mm in diameter and, excluding the IO base pins, is 72 mm tall.
References: Datasheet, 1040 & 1043. Type DL35 was first introduced in 1946.