Used BBE 411 Sonic Maximizer
The BBE 411 Sonic Maximizer was a tool used widely from the late '80s to the late '90s. It is a frequency time alignment device that works especially well for the broad range of the bass guitar. This one was bought new in the late '90s, rack kept, and used sparingly. A link for the original manual is provided should you want to go in depth on what this piece of gear does.