It looks to be a "Sidney Brown" accordion. The reason I say it that way is because I have have heard sories where the original face plates of other accordions ( such as Monarchs or Sterlings) were used to build a new instrument around them.
I don't really think that's the case here, but the accordion has had some restoration work done on it.
The valves ( "flappers" ) look to be new and it looks as though it's had a fresh coat of paint put on.
All that to say, yes , I believe it is a "Sidney Brown". It has been cleaned up, and touched up, and looks very nice. You should also know, that this instrument most likley has Hohnor reeds inside. That's all Sidney used in his accordions back then.
Jude