Order Vintage Brass and Jade Abacus with original box

Vintage brass Abacus on a real genuine jade back plate.
In perfect condition!
Comes in original box (box has a tiny bit of wear) and instruction book.
Name plate says Hong Kong 1991 so I'm assuming that's the order make year but I don't really know.
Measures 5.5 inches long by 2.5 inches wide by .75 inch thick.