The 35Z4GT is a half wave rectifier and was designed for television use. It would feed a 40 µF reservoir capacitor through an effective series resistance of 100 Ohms. The octagonal outline to the Type designation looks very much like an RCA design.
The Elpico logo and Type designation, added in paint.
The box anode is much wider than the front to back dimension.
The wide glass tube envelope is 28 mm in diameter and excluding the IO base pins and spigot the height is 71 mm.
