Type RZ1-150 is a directly heated (4 V at 4 A) full wave rectifier and is rated at 1,000 V, 150 mA, which is no more than a type 5R4GY.
The exhibits we have of Type RZ1-150 all differ in height. This is the shortest at 140 mm and RZ1-150 is the tallest at 170 mm. The variation seems to be in the length of the pinch stem not the electrodes.
The serial number on this valve is 2935 - so more than a few were made.
Face view of one anode.
The two rectifier sections side by side.
The lower mica showing the ribbon filaments. The filaments are M shaped. The filaments are intact but at 4 Volts the filament takes 5 Amps without glowing - something must be shorted.
The top has a double insulator and above the top one can be seen the filament tension springs.
The anodes are secured in the lower mica with the filament loops passing above to the top insulator.
The wide glass tube envelope is 52 mm in diameter and, excluding the L4 base pins, is 141 mm tall.
References: Private communication & 1043. Type RZ1-150 was first introduced in 1934.