switchboard part? need identification

[RotaryOne]

Hello forum members,

I'm unsure where I should post this.  Is this part of a switchboard?  It measures about 4" x 1 1/4" and 1/4" thick.   It looks like lamps connect to it and can be screwed into a panel.   Stamped 30C and it looks to be bakelite.
Any information is appreciated.

[RB]

Hi.
No wizard here, but could that be a plate for the op set to plug into? just a guess...

[Babybearjs]

whats the backside look like?

[Victor Laszlo]

It holds either lamps or keys, and is used on a PBX equipment frame.  Lots of different possibilities for the designations.  Here are some examples:

BY = busy

R = release

T =

H = hold

The backside looks like the front side, except for holes that accept the mounting screws for the individual lamps/keys/buttons.

Note the OCD of the Bell System in requiring FOUR (!!!) # 6 FH machine screws to resist earthquakes.