The Galactic Empire: An Empire Reborn
Imperial Officers' Manual
Major Revision: 2.0 – 2008.10.31
An adaptation of the pre–Endor document and policies.
RIP
... An ISB Commander's Rank Insignia ...

An ISB Commander (ISB–CM) always acts as a shipboard Head of Security.

The rank of ISB Commander is the minimum rank required to act as the shipboard Head of Security for a large-scale vessel of the Imperial fleet... Onboard smaller vessels, exceptional Heads of Security may be promoted to this rank.

An ISB Commander is granted level 90 X access in #Galactic_Empire.