The 65EX5 is a mystery. It is a full wave rectifier on an IO base. It is probable that 65EX5 is a production code and not a Type designation
The image above sent in by Baptiste Hobbe shows a Type 83 rectifier with the code 65EX5 on the base cap. The 83 is a mercury vapour rectifier on a UX4 base and so different to this exhibit.
The anode side elevation of our mystery valve.
The wide glass tube envelope is 29 mm in diameter, and excluding the base pins is 67 mm tall.
Updated April 05, 2017.