Sure looks like the Gritzner (White, Kenmore, Pfaff) machines. At least the accessories look to be for all White machine, albeit different ones, unlike the White top clamp feet that came with your Singer 600. I do see at least two high shank feet in the box. One is in the upper part on the far right and the other in the bottom section on the far left. My Pfaff 139 (G-Z) uses high shank feet.
I also see a hemstitching fork. I tried the one I have once, but wasn't pleased with the results.
Janey - Neat people never make the exciting discoveries I do.