I have a wonderful 900 silver bowl, and my first impression of it was Mexican (I have a few other bowls by Sanborns which have near-identical floral motifs), however I'm unfamiliar with the hallmarks! I even had my silversmith look at it, and he came to the same conclusion that I did - that it's most likely Mexican or South American. The piece is stamped 900, and has a hallmark of a rooster, and a crown.
I have a few more photographs of the piece here - http://imgur.com/a/f2CZL#0
Thank you for your time,
Joshua