Dear Tim,
If you have not tried before, you can write to:
Graafsmuseum
St. Elisabethstraat 10A
5361 HK Grave The Netherlands
Or -info@graafsmuseum.nl. And there is a link on this mentioned site as well, to "Bommeltje", also a website where you can walk through this town's history and maybe ask for pictures, and further information about your ancestors and their jeweller's store.