[Arran]

The grille in that set is not in bad shape compared to many of those 20s, repairing the veneer should be fairly easy as it's chipped out parallel to the grain. So a straight sided patch, followed by gluing, clamping, and then careful filing, and sanding around the openings, and the patches should be almost invisible, as long as you pick veneer with similar grain, and colour. I'm not sure what species of walnut was used in the front panels of these sets, I think it was French walnut, but Steve could tell you.
Regards
Arran