Thanks, Pete.
Sorry, I should have said, I bought the bowl at least 5 years ago whilst visiting, and have been looking through American books, catalogues, eBay listings and on-line collections ever since.
My first guess was Blenko, since it's a good match for their amber colour.
Haven't found anything even close and am getting desperate!
I don't usually ask for help on newly-found items, unless I know that someone's actively researching that area. If there's material out there to be read, I like to try and work things out by myself. It keeps me out of the pub.
If I posted absolutely every item that I haven't yet identified, I'd be hogging the whole forum...