The juvenile gangs were called the [Purple Hearts] (originally the Night Prowlers), the Blue Devils, the Black Tigers (the Apaches), Green Valley (Happy Valley), and Chalk Hill (Rose Hill).
This episode was based on [The Big Juvenile Division] from the radio drama of the same name. At the time, Ed Jacobs (Barney Phillips) was partners with Joe Friday before Frank Smith came along.
Somewhere along the line, Joe Friday is promoted to Lieutenant (from Sergeant) and the shield shown at the beginning of the program reflects that promotion . . . but it is still badge number 714.