RCA consol type 51 jewel lamp.

[RLK1]

I have a RCA Victor Model A-108 Superheterodyne. This has two turntables and a radio in a Mahogany consol. One the bottom front of the consol is a small jewel which from the schematic looks to be a light. One the schematic it is called a "Type 51 Jewel Lamp" I want to put a light into it as it was. It is missing both the housing and bulb which looks like it was cut off some time ago. Would anyone know the correct voltage to the bulb? I cannot tell from the schematic. I figured I could wire a light kit to the cut off wire and place into the slot behind the jewel.

Thanks for your help