The 25Z6GT is a pair of rectifiers in a single envelope with a common heater connection. This construction offers a flexibility in circuit design. The 25Z6GT can be used as a half wave rectifier with both sections in parallel. A full wave rectifier by joining the cathodes or as a voltage doubler.
Electrically the 25Z6GT is identical to the 25Z6 and 25Z5.
The Mullard logo and Type designation is printed onto the glass. The original RCA identification is etched into the glass.
The twin rectifiers and Made in USA on the IO base cap.
The insulated heater wire passes through the cathode tube several times.
The anodes are stitched together.
The wide glass tube envelope is 29 mm in diameter, and excluding the IO base pins is 62 mm tall.
References: Data-sheet & 1040. Type 25Z6GT was first introduced in 1938.