Very early ladys wristwatch

I believe this is a very early ladys wristwatch. No signature (haven´t checked under the dial). Case made of silver and gold + niello. Winding crown to the left. Diameter approx: 27 mm excluding windingcrown.

Case has a mark. It´s hard to read but i believe it´s one letter +"... & Co"
I am searching after any further information .................

Regards
Peter