The 210RC from Cossor is a high impedance triode broadcast receivers. The original Point One series introduced the RC valve for resistance capacity coupled circuits and this exhibit is post 1929 when the 'New Process' coated filament was introduced, the box linked to this exhibit is an earlier design. Also the new designs went to a box anode with mica supports. The earlier valves had a pointed anode. Between the Stentor TwoTin Hat anode design and this vertical anode we have an early 210RC with a horizontal box anode that predates the 'New Process'.
The bright anode is broad and tall but only about 5 mm from front to back.
The filament is a single inverted V hairpin. The grid extends below the anode which has ridges pressed into the broad face to make it rigid.
See also610RC with the 6 volt filament. The range also included the 410RC four volt version.
The balloon envelope is 41 mm in diameter, and excluding the B4 base pins is 83 mm tall.
References: Datasheet, 1043 & 1040. Type 210RC was first introduced in 1929.