2- shelf brackets will support 5 inch wide piece of glass.
Brackets appear to be in fine shape. They have a couple of tiny specks under the glaze that only show up over time, typical for items of the same age. They are showing nice age, some light crackle under glaze.
Glass shelf can be purchase at local glass dealer.
Brackets will need metal or wood clips to slide into the back slot to attach to wall. Wood clips can be made to fit slot. A tapered piece of 1/4" plywood cut to fit slot works just fine.