Those braces normally have cocobolo rosewood handles. Stanley spent
a brief period making aluminum tools. They were mostly for trade schools,
I think. Your brace would date from 1926 thru 1933-ish. When in decent
condition (like yours), some of these oddball aluminum tools are more
valuable than the equivalent standard model. It's just a collector thing.
So you may want to research the current market value for your 903A.
My best guess is about $100, which is slightly higher than the normal
brace.
Also, please don't "restore" the tool. Clean the grime and grease it,
but don't strip the remaining nickel plate or sand/polish the aluminum.
That totally ruins the value to collectors.