This is a curious prototype that started out as a US-made flat-tassie sterling silver crosshatch grid FP. It appears to have been coated with some yellow colored material that got into the lines of the grid pattern.
You can get a better idea of what's on the surface from these two close-up pictures of the tassie area.
Note the in spite of the yellowish color of the squares in the pattern, closer inspection near the tassie reveals its shiny sterling silver base metal.