Perhaps I said that badly. "If all the clocks agree at satellite facility A, and all the clocks agree at satellite facility B". I'm not comparing clocks at A

Perhaps I said that badly. "If all the clocks agree at satellite facility A, and all the clocks agree at satellite facility B". I'm not comparing clocks at A with clocks at B. Second, I was thinking of labs perhaps tens of km apart. You can have people at the center, and at satellite facility A, and at satellite facility B.