The other reason I really think it's white is because if it's silver colored, then what color are the details? Black? That's just not how circuitboards are made, and all the evidence points to this actually being a manufactured pcb.
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I think the traces are covered by the white soldermask, showing through the white, like a typical circuit board:
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So will the new cards you are making have the details that are in your words, under the white solder mask?
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