<Tr> <Td> </Td> <Td> FOCS </Td> <Td> Federal Institute of Metrology METAS, Bern, Switzerland </Td> </Tr> <Tr> <Td> </Td> <Td> NPL - CsF2, Yb and Sr+ ion clocks, Sr lattice clock, 4 hydrogen masers </Td> <Td> National Physical Laboratory, Teddington, London, United Kingdom </Td> </Tr> <Tr> <Td> </Td> <Td> NIST - F1, NIST - F2 </Td> <Td> NIST laboratories, Boulder, Colorado </Td> </Tr> <Tr> <Td> </Td> <Td> Department of Defense master clock </Td> <Td> United States Naval Observatory, Washington, D.C., United States </Td> </Tr>

Where is the official si atomic clock located