Hmm too late for this one... my sister is currently working at a soil testing company so I might have had a chance of guessing that!

What's so difficult about beating brass? I've done it before with copper to make end caps for a boiler. Is it just that the material is harder than copper? (Edit:) I guess it's harder to anneal brass without accidently melting it, but hand beaten brass bowls do exist:
Medium Hand Beaten Brass Coloured Singing Bowl 18cm | eBay