I do not believe Gahr worked on two separated layers then joining them, but the reasons for Gahr requesting a bilaminated silver alloy to his provider could be few :
1) since the inner layer is softer, to make the engraving job easier ? (my preferred one)
2) to save silver if compared with an alloy with more percentage of silver ?
3) to prevent engraving area from oxidation ?
Anyway I see no reason to believe lab result uncorrect, since it was performed on several rings even and it paradoxically kill the die cast theory.
Since double band is never visible, it means that Gahr received blank silver bar already bilaminated, more likely the same way SS cap eagles/skulls factories received cupal alloy ready to be impressed?.(during pre-war period).
