The 1807 rectifier is a directly heated device from the early 1930s. The construction looks very similar to the Mullard DW3 & DW30, the DW30 is rated for 500 Volts.
The anodes have a wave pattern embossed on them to add mechanical stability.
A glass I section at the top holds the filament tension springs.
Another view of the top glass support. On the dome can just be seen the Type designation.
The balloon envelope is 52 mm in diameter, and excluding the B4 base pins is 111 mm tall.
Reference: Data-sheet. Type 1807 was first introduced in 1932. See also1932 adverts.
