This is a strange construction for a decanter; the neck has two spouts, the stopper is drilled through so that when you align stopper and neck you can pour without taking the stopper out.
The cutting is reminiscent of Tusend Fönster/ thousand windows - but I have been unable to place it in time or in series.
The marking is Orrefors 04879-921 - but I am not sure @ all about the 0487 bit - it could also be 0402
Does anyone have further details of this product?