The "Real IRA" are referred to throughout Seasons 1 and 2 as the "True IRA". Something that (as far as I know) never existed. From Season 3 onward they correctly call them the "Real IRA".
In the final scene in the cemetery when Jax is standing at his father's grave, the same 3 or 4 names can be seen on almost all of the other tombstones when the camera pans back.
A closeup of the white dove sitting on the Highway 221 North sign, the leather jesses tethering the dove to the sign can be scene around its legs.
Around minute 32, after Jax and Deputy Chief David Hale have a discussion, Jax smashes a cell door with his foot. The shock opens another cell's door and we can see a staff hand catching the door to prevent it entering more into the camera field.
The sign with the dove shows 221 to be a US Highway from its shield. US221 is on the east coast. There is a SR221 in California known as Napa-Vallejo Highway, but it uses the green California State Route sign.