Knobs, Bakelite or not?

[Vincent1]

Hello,
first post.
I have been given a 'Sterling Telephone and Electric Co Audio Frequency Power Amplifier'
(circa 1924 based on bbc stamp on the 'R' type valves)
It was found in a skip (wooden case removed unfortunately) and finder gave it to me..

My question is about the knobs.. tuning and binding posts pre restoration.

Does anyone have one, or similar item from Sterling Telephone etc, and know if these are likely to be 'Bakelite'
I ask because some are a rich dark brown and some others lighter browns..one almost tan.. (as if faded by the sunlight)

Also the smell is a very distinctive 'burned rubber' smell (I recall formaldehyde as a bit sickly and cloying)
So perhaps some sort of urea formaldehyde resin ?

I heven't done the hot pin test yet..

If they are Bakelite (or even if they aren't) does anyone know a good way to darken them to a close to original colour ?

I could post photo or two but not sure if permitted with this being first post etc..

all best
vincent

[Vincent1]

Update.
Knobs and binding posts are in fact Ebonite (hard rubber)
Confirmed partly by smell test, high magification examination.. behaviour (probably long exposure to sunlight, water and weather)
and really confirmed after on-line search of patent office revealed an identical Sterling Telephone Co. etc knob being detailed as 'ebonite'..

So now I shall set aside for re-colouring..
Have attached image of item (minus the LS2's)
Upper left binding post removed for examination..

Now to try and find out original main panel finish..
Matte, slight sheen or polished.. from what I've seen in the few web images I've found I think matte..

Bomber County may know as I understand he saw another rather interesting, and seemingly untouched, Sterling item recently ?

all best
v