Great. I've got to change the access codes out of Cryo A again! Like I've got nothing better to do. I think Grassi just likes to make work for me. I'll set the new code to 45100. That should be easy enough to remember.
The code 451 is a reference to the original System Shock (among others), and is referenced in several other games including: Thief, Deus Ex, Deus Ex: Invisible War, Deus Ex: Human Revolution, Deus Ex: The Fall, Deus Ex: Mankind Divided, Deus Ex GO,Sanitarium, Bioshock, Bioshock 2, Bioshock: Infinite, Gone Home, Firewatch, The Novelist, Dishonored, Dishonored 2, and Prey (2017). The code itself is originally a reference to a code for a Looking Glass Studios office.