This striking brooch is unique - I've never seen one like it! My step-grandmother told me that it's sterling, and I'm inclined to believe it, because the keeper pin in particular shows verdigris. The keeper has a pin on its back, the llama has a pin on its back and the two are connected by a fine chain "leash."
There is no maker's mark, but there is a number on the back that looks like "925."
Featured in the "Catherine's Eclectomania" Treasury List: http://www.etsy.com/treasury/NjQ2NTk0MHw1NTg0MjI5NzE/catherines-eclectomania