The DW2 is a directly heated full wave rectifier.
The DW2 is rated to work with no more than a 16 μF reservoir capacitor.
The dome carries the identification of both manufacturer and type.
The envelope is - ;mm in diameter and, excluding the base pins, is - mm tall.
References: 1931 data-sheet. Type DW2 was first introduced in 1930. See also 1930 adverts.