In Jedi Night, a stormtrooper refers to himself as LS-261. The Imperial ISB Agent Alexsandr Kallus is known as ISB-021.

In Star Wars Rebels, Imperial Officer Cumberlayne Aresko goes by the operating number LRC-01. In most cases, especially stormtroopers, the two letters are “TK,” (likely referencing Star Wars), but there are many instances of personnel, including stormtroopers, with designations other than TK numbers. Throughout the non-movie material of both canon and the original Star Wars timeline, the Expanded Universe (now known as Legends), Imperial operating numbers consist of a set of letters followed by three or four digits. Conversely, Imperial stormtroopers are enlisted soldiers who rarely have any need of their birth names after they have joined the Stormtrooper Corps as they lose their individuality to the service, working as a mirror image to the clone predecessors who fought to find their independence when it had been denied of them. Fan-favourite Clone Captain Rex was born as CT-7567 however, early on in the Clone Wars, CT-7567 somehow earned the nickname Rex, which became his primary moniker for the rest of his life. The clone troopers who came before the stormtroopers were not given names at birth but were given identification codes that resemble TK numbers. In Star Wars: A New Hope, Han Solo is asked for his operating number, and while that might seem simple there is a rich history behind these codes.

In short, the TK numbers are simply a specific Imperial code used to identify military personnel. Related: Star Wars: Does Stormtrooper Armor Actually Provide Protection? The TK numbers are first referenced when Luke Skywalker infiltrates the Death Star disguised as a stormtrooper that is known as 'TK-421.' In The Mandalorian, a tense scene shows Din Djarin, disguised as an Imperial Juggernaut Pilot and sneaking around an enemy base when an Imperial Officer named Valin Hess asks him for his TK number. In Star Wars: The Force Awakens, Finn used a variation on a TK number as he was originally known as 'FN-2187.' So these numbers have always been present, but what do they mean for the Empire, and how does the idea behind them change for the First Order?

Here's everything you need to know about TK numbers in The Mandalorian and beyond. 'TK numbers' have existed in the Star Wars universe since the first movie in 1977 but they have received new attention after they were referenced in The Mandalorian season 2, episode 7, 'Chapter 15: The Believer.' The numbers have always been important but have gained notoriety over the years as the Star Wars expanded universe has continued to grow one way or another, even after Disney decanonized large amounts of it.

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