Electric symbols

[electrolitic]

I received an electric single line diagram drawn in USA where it appears two small circles close to a low voltage circuit breaker. Inside one circle is written EO. Inside the other, DO. What do they mean?
Thanks.

 

[dpc]

EO could be "electrically operated"
DO could be "draw-out"

If you post an image of the actual drawing, it might help.

 

[wolf39]

I could never understand why the IEC is unable to standardize electric symbols. Even worse is the fact that in a library you have to bend your neck left and right to recognise book titles.

Wolf