I wanted to let you know that your question has been viewed, I will send this to Robert. He will pick this up as soon as he signs on to the site. I am going to opt out so he can do that.
I am sorry I did not find anything that would give me a value to give you on this before your auction. I am going to opt back out so Robert can pick this up, he is very good at items like this.
So sorry to have missed this; for some reason it failed to show up in my list of Active Requests.
Here's a quick answer in case this is still active and relevant.
This bowl is a very nice antique example of 'Persian' (Arab) mixed metal work, copper, white bronze or silver and brass, often referred to as Cairoware, though made in a number of centers other than Cairo throughout the Middle East such as Damascus, Jordan and Turkey.
The design is based on those that have remained almost unchanged since the Mamluk era of the 11th century, and a style that's referred to in the decorative arts as "Mamluk revival" most of which dates to the late 1800s or early 1900s, which is almost certainly the age of this piece. Although impossible to see exactly on this one, the calligraphy is typically an Islamic proverb to do with human virtue such as patience, forbearance and fortitude.
This is a nice example with a lot of workmanship and detail. I would give it an auction value in the range of £150- £250.
Full retail value £450.
Hope this helps!