6. La Eme
La eme is the Spanish for Mexican Mafia. Despite its name, the highly organized criminal gang did not originate in Mexico. They are US criminal prison organization. Other gangs like MS-13 and Florencia 13 use the number 13 to show their affiliation to the Mexican mafia (M is the 13th letter of the alphabet).
The gangs primary symbol of an eagle and a snake atop a flaming circle over a crossed knife is found tattooed among hardcore member’s torso. They also use the images of a black hand.(source)
The Nortenos or northerners are loosely affiliated gang that pay tribute to the Nuestra Familia within the US Federal and State correctional facilities. Nortenos use the number 14, as it represents the 14th letter of the alphabet, the N. Sometimes it is tattooed as XIV or in a fusion of Roman and Hindu-Arabic numeral X4. Some Norteno’s will tattoo themselves with four dots.(source)
8. Aryan Brotherhood
The Aryan Brotherhood is a white supremacist prison gang that originated in 1967 in the San Quentin prison in California. The gang formed as a protective shield against the attacks of Mexican and Black inmates. They are known as Alice Baker, AB, and The Brand. According to FBI, the gang makes less than 0.1% of the prison population but are responsible for 30% of the murders in the federal system.
The clock with no hands is a subtle tattoo indirectly suggesting that the inmate is in for a long haul. Prison inmates who are looking at a long sentence do not want to be reminded of the passing time. They view the passage of time in a different perspective, for them, there is no meaning in counting the days or hours. So, they embed a tattoo of a clock with no hands.
The clock tattoo has several variations. They may be the face of a wall clock or a grandfather clock. They may even be a wristwatch tattoo with straps and all. Clock tattoo is quite popular, always look to see whether they have hands to ascertain the real status of the wearer.(source)
10. Five Dots
The five dots tattoo is generally found on the outer surface of the hand, between the thumb and forefinger. The five dots are sometimes known as quincunx and stands for the time done in prison. This is an international tattoo, common among European and American prisoners. The four dots on the outside symbolically mean the four walls of the prison and the dot in the center stands for the inmate.
However, five dots on other parts of the body signifies that the individual is associated with People Nation Gang (a Chicago-based gang).
Interestingly, the famous scientist Thomas Edison had this pattern tattooed on his arm.(source)