The R Type was from the beginning a hard vacuum valve. Hard pumping with the vacuum pumps of the day was a long process and to remove adsorbed gasses from the metal parts heat was applied. This was successful but not complete. Over time, and when hot in use, gases would be released and bombard the electrodes. The use of gettering both shortened the pumping time and, after the valve was sealed, the getter would continue to take in gas molecules that evolved from other electrodes. Here we have a beautiful gold colour that is the result of using phosphorus as the getter. Only later bright emitters were gettered and this example is probably from 1923 or 1924.
The Marconi Osram Valve logo is etched into the envelope but is hard to see. The nickel plated brass base shell was used up to 1924 and then replaced with the cheaper Bakelite. SeeR Type for the later version.
The filament strand has been coiled on the left to act as a spring. The right hand end remains straight.
Close inspection shows that the filament is not continuous but unusually has not shattered. The grid is an 11 turn helix of 0.25 mm wire with an overall diameter of 4.24 mm. The nickel anode is formed into cylinder 15 mm long and 10 mm diameter.
This image focuses on the spring end of the broken filament.
The balloon envelope is 46 mm in diameter, and excluding the B4 base pins is 98 mm tall.
References: Private communication, 1005 & 1003. Type R Type was first introduced in 1916. See also1916 adverts.