From "Central Power Pistols" (Still, 2007), 1906 Army Test has "GESICHERT". The word is on the lower position. It's not mentioned the wording being white or not on that rare variation. I assume it is. The GESICHERT in the "normal" upper position became standard in 1908, and it's in white..... actually looks yellow/brown after so many years.
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It's also on 1906 Navy. Not sure which one was earlier.... 1906 Navy, or 1906 Army Test.
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Anyway, it's definitely not a Mauser nor WWII only feature.
