I spent the 80's working on UNIX starting at Western Electric and Bell Labs in Illinois and then Pyramid Technology in California. I spent the 90's working on Windows NT with Digital Equipment Corporation and Veritas Software in Redmond.
At one time or another each of these license plates were on my car. During 1993 I had Washington UNIX on the front and Washington NT on the rear; I enjoyed parking my car in the Microsoft visitor's parking lot that way.
But recently (with my wife's permission) the precise time & frequency hobby has taken over both cars...
UTC is Coordinated Universal Time, often approximately called GMT or Zulu time.
1420 MHz is the ground state hyperfine transition frequency of a Hydrogen atom. You may also know of it as the 21 cm line (universe background radiation, SETI, etc). The actual measured frequency is 1 420 405 751.768 ± 0.002 Hz.
9192 MHz is a ground state hyperfine transition frequency of a Cesium atom. You may know this as the modern definition of the length of a second. The defined frequency is: 9 192 631 770 Hz.
Other magic frequencies are 6 834 682 612.904324 ±(4)(7) Hz for Rubidium, Rb87; and 40 507 347 996.84159 Hz ±(14)(41) for Mercury, 199Hg+.