First Appearance: Captain America (vol. 1) #170 (Feb. 1974): "J'accuse!"
Number of Appearances: 1
Enemy of: Moonstone
Employer: natural history museum
Occupation: security guard
Note: killed by Moonstone while stealing moon rock
Jack was a security guard who worked at a natural history museum in Nashville, Tennessee.
Jack was on duty one night when Lloyd Bloch broke into the museum in order to steal a rare moon rock on display there. Jack and another guard confronted Bloch, pointed their guns at him, and told him he was under arrest.
Lloyd Bloch threw his heavy box of tools at Jack's head. Bloch did not actually intend to kill Jack, but Jack died from this assault, something Block realized instantly. Block was then desperate to escape because he did not want to face a "murder rap."
Bloch, fleeing, punched Jack's partner. Jack's partner thought to himself: "...must... stop... him...! He's... murdered.... Jack!"
Jack's partner then shot at Bloch, but only managed to shoot the moon rock Bloch was carrying. The rock shattered and its strange energies (from the Watcher's Blue Area on the moon) caused it to infuse with Bloch and give hims super powers.
Using his new power, Bloch incinerated Jack's security guard partner and then fled. Block later adopted the costumed identity "Moonstone."