Royal Institute for the Study and Conservation of Belgium's Artistic Heritage
Object search for beurs reveals many many interesting finds, particularly this gem: Object 10359
The photographer (bless him!) took a picture of the side of the piece:
Take a look at the frontal pictures, particularly the drawstrings. I wonder if those large turks-head knops are not in fact part of the drawstring, but there to aid opening the bag.. in which case the drawstrings appear to pass through a hole in the center of each.