An experimental valve from M-OV, the E2185 looks to be a triode but no other details are available.
The serial number is 19 and this would have been supplied to the UK government or one of the armed services.
The lower mica reveals an indirectly cathode and single grid.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 77 mm tall.
Updated October 14, 2015.