The Fermi National Accelerator Laboratory, outside of Chicago, is home to the most powerful particle accelerator in the world. One of its biggest successes was the discovery of the last of the six quarks, the top quark, in 1995. (They also discovered the bottom quark in 1977.)
When I worked at Fermilab (03-04) I did a fairly comprehensive survey of physics-related vanity plates among the staff and users. The number of ways people referenced “quark” on their plates approached the number of ways people spell “Britney Spears” in Google.
Physicist Michael Tartaglia has owned “DO TOP 1” since he came to the lab in 1990. “I thought it would globally advertise Fermilab’s mission to study the top quark, and locally advertise my affiliation with DZero [one of the particle detectors],” he said. (He no longer works with DZero, but the ring in “DO” doubles as a letter O, making "DO" a verb.)
Particle physicist Rajendran Raja has had “TP QUARK” since 1995, the year of the discovery. “I was the top quark convener in DZero from 1990-1994 and felt proud of the achievement of the whole collaboration,” he told me.
Particle physicist Harry Cheung got “CQUARK 1” in 1997. He works on an experiment called FOCUS, where they study the charm quark, “though it could stand for ‘See Quark 1,’” he said. “CQUARK” was not taken, but adding the 1 actually reduces the licensing fee.
Oh, the equivocating. Theorist Zach Sullivan kept it simple: “QUARK.” When he picked it up around 10 years ago, the people at the registry apologized for misspelling “quirk.” But at Fermilab, there can be no misunderstanding.