The Crying of Lot 49, Chapter 1
a Mexican city on Mexico's Pacific coast. Pynchon lived in Mexico during parts of the 1960s.
Pynchon's alma mater.
(1836 – 1892) was an American financier, who became a leading American railroad builder and speculator. In his lifetime and for a century after, Gould had a firm reputation as the most unethical of the 19th century American businessmen known as robber barons. Wikipedia
"Mucho más" is common Spanish phrase, meaning "much more."
Pachucos were Mexican American youth who developed their own subculture during the 1930s and 1940s in the Southwestern United States. They wore distinctive clothes (such as Zoot Suits) and spoke their own dialect (Caló). Wikipedia Zoot suits appear a few times in Gravity's Rainbow.
chingas and maricones
Spanish slang for "fuck" and "faggot".
One identity adopted by The Shadow, a character of pulp fiction, radio shows, and comic books. Cranston was a wealthy young man about town. Wikipedia
LSD-25, mescaline, psilocybin These hallucinogenic drugs are also mentioned in Gravity's Rainbow. It remains an open question as to whether and to what extent Pynchon took or was influenced by them. 
The Rorschach inkblot test (Pronounced roar-shock) is a method of psychological evaluation. Psychologists use this test to try to examine the personality characteristics and emotional functioning of their patients. Wikipedia
a face is symmetrical like a Rorschach blot
In the graphic novel, Watchmen, written by Alan Moore, there is a character named Rorschach who wears a mask with a Rorscach blot on the front. Moore is a self-professed Pynchon fan: he referenced V. in V for Vendetta and has mentioned Gravity's Rainbow in interview. It is possible, not to say probable, that Moore was inspired by this line.
The TAT is popularly known as the picture interpretation technique because it uses a standard series of 31 provocative yet ambiguous pictures about which the subject must tell a story. It was developed by American psychologists in the 1930s. Wikipedia
Dr. Fu Manchu is a fictional character, an evil genius of Chinese origin, first featured in a series of novels by Birmingham author Sax Rohmer during the first half of the 20th century. Wikipedia
Perry Mason is a fictional defense attorney who originally appeared in detective fiction by Erle Stanley Gardner. Mason was portrayed by Raymond Burr in a television series which ran on CBS from 1957 to 1966. The typical plot involves Perry Mason unmasking the actual murderer in a final dramatic courtroom showdown. Wikipedia
The Profession v. Perry Mason
Roseman may be trying to undermine Perry Mason by arguing that the dramatic courtroom twists in the TV show are actually uncommon in the American legal system.
Bornando el Manto Terrestre
Remedios Varo (1908 - 1963) was a surrealist painter. Wikipedia
Bill Brown notes that "Pynchon saw Bordando el Manto Terrestre when, as part of the first full retrospective of the painter's work, it was displayed at the Palacio de Bellas Artes in Mexico City in 1964, a year after her death at the age of 55. Painted in 1961, el Manto (oil on masonite, roughly 40 by 48 inches) is the central panel in an autobiographical triptych. It is possible that Pynchon, writing Lot 49 in 1965, recalled the painting from memory or incomplete notes, and not with a reproduction of it set in front of him. He gets a lot wrong."