Rex Tyler's Journal (Earth-2: Post-Crisis)

Rex Tyler's Journal is written in equations that leads to the map of the ISA Headquarters.

History
In 2010, Rex Tyler was hunted by the Injustice Society of America and he sent the journal along with the remaining property of the Justice Society of America to Pat Dugan in North Hollywood. Soon after he left, he and his wife was attacked by Solomon Grundy and died.

After Courtney Whitmore became Stargirl in 2020, she started recruiting new members for the JSA and Rex's son Rick was one of them. Courtney, Yolanda and Beth later helped Rick uncover the truth of his parent's death. Rick then joined the team and seek revenge for his parents. As the Rick's presence was discovered by Pat Dugan, he decided to give the journal to Rick hoping he could solve it. However, he and Chuck, an A.I. version of Charles McNider are unable to solve the equation in the book.

Later, Rick found out only one number is needed to fill in to solve the equation. Rick was frustrated and Pat asked him if his father ever had a special number in his mind. Rick said he tried his birthday, Rex's father and his mother's birthday which are incorrect. Rick than made a breakthrough and tried 1966 which represents his father's favourite car, the 1966 Mustang. As Rick solved the equation, he showed it to Chuck and a map of the ISA Headquarters is displayed. With the map, there are able to infiltrate the tunnels and finally being able to be offence in the War Against the ISA.