[Al_The_Man]

Generally the proprietary encoders are used on the AC (Red-Cap) servo's.
The DC generally used a standard quadrature encoder.
Not sure of your description of the encoder?
Would need the Fanuc model number to confirm, from that the type and resolution could be known.

[bmn]

Thanks very much for the reply Al !

The control was an old Fanuc 0MB / 6MB...if it can help an there was no sticker on the encoder from what I could see, it was laser marked on SS encoder housing...
" BRUSHLESS
TYPE
INPUT
TAMAGAWA"

And it is clearly way off center, to the side of what looks like the bearing flange/housing, but could be part of a larger encoder...

Please, how would you remove the black cap from the motor in a non destructive way ? to take a closer look at the encoder ?

I have tried to pry it open but it seems to be glued, and I am afraid of using heat around sensitive components.