The Guardian-Vexor was given as a prize in an early EVE lore event, the Gallente Frontier Tours Limited events, which was held in mid-2004. There were 50 given out in the form of blueprints that each had 5 runs, and two weeks later 5 more. The events consisted of somehow hauling large bulk of npc goods to the GFTL npc corporation in Stacmon.
It has been said only around 20 remain now, and that Entity has 5 of these. One Guardian-Vexor was destroyed in December 2012 and one was destroyed in 2014. One was sold in 2013 for 85 bn.
CCP planned to give out 3 new GVs as prizes in a Somer Blink lottery in 2013, but after receiving criticism these were changed to Stratios Emergency Responder.