NASA is celebrating a 29-cent Pluto-themed postage stamp stuck to the side of the New Horizons spacecraft that has traveled nearly 3.5 billion miles from Earth.

NASA says the 1991 stamp that carried the message “Pluto Not Yet Explored” helped inspire the New Horizons team. The team stuck it to the spacecraft shortly before it launched in January 2006, and NASA says the U.S. Postal Service officially canceled it after New Horizons made its flyby of Pluto last July.

Guinness World Records recognized the stamp at Postal Service headquarters in Washington on Tuesday for the farthest distance traveled by a postage stamp.

The stamp and New Horizons’ next stop is a Kuiper Belt object 1 billion miles beyond Pluto, where the spacecraft is expected to arrive in 2019.