Symbolism, Imagery, Allegory
If symbols could be foils for symbols—and why not?—then the Edfrank jewelry could be a foil for Childan's American "antiques": both are American, but the antiques are from the past, whereas the jewelry is from the present. Paul Kasoura makes this clear when he compares the jewelry to a medieval relic, which isn't that far from those American antiques: "This is alive in the now, whereas that merely remained" (11.89).
On top of that, if the antiques are largely from the Civil War (a time when America was being torn apart), this new jewelry comes out of a new melting pot. It's designed by an Irish-American (judging from the name McCarthy), made by a Jewish-American (Frank Frink), and honored by one of the new Japanese-Americans (Paul Kasoura, who is in San Francisco for political, not military reasons).
Perhaps it's for that reason that Tagomi can use one of the Edfrank pieces to transport himself to a world where the US won WWII. That is, unlike the "antiques," the Edfrank jewelry is both an authentic expression of contemporary Americanness, and it's also a sign of the American identity that can come out of this history. Tagomi notes this himself when he thinks that this jewelry has some animating force: "the first stirring of light is suddenly alive in the darkest depths" (14.50). Out of a terrible history, this new future is coming in to being.