Looks like a cup holder a Daimyo would have on a pimped out Palanquin! It's metal arm would clip on the window edge and he could hold his drink while bobbing along. (Circa 1970's US Auto Cup Holders for those not old enough to remember).
LOL, maybe too easy. I will have a hunt for something more challenging. I like the coffee cup holder idea BTW. I'm taking the holder to sell at the next Birmingham arms fair in June, so if anyone likes it, let me know before it goes!