The 33GY7A is a combined line output valve and efficiency diode in a single envelope. The 33GY7A differs from the 33GY7 only in the construction of the anode, electrically they have the same ratings.
This valve is of Japanese manufacture but no makers name is visible.
The efficiency diode (half wave rectifier) is on the left and the beam tetrode on the right.
The anode of the efficiency diode seen face on. The bundle of ceramic insulated heater wires can be seen above the top mica.
The bright beam forming plates can be seen where the anode does not go completely to the mica supports.
The wide glass tube envelope is 38 mm in diameter, and excluding the base pins is 67 mm tall.
Reference: Data-sheet. Type 33GY7A was first introduced in 1967. See also1967 adverts.