Resident Evil Requiem briefcase code

Puzzling out the briefcase code in Resident Evil Requiem can take a little bit of legwork. Similar to the scavenger hunt you also start in the S.T.A.R.S Office, there are some clues littered about that room that tell you where to find the code for the briefcase. It's only three-letters, but it's not really the kind of thing you want to brute force, especially when the answer is so close at hand.

I'll explain below what the briefcase code is if you're in a hurry, but also how to get the code if you were struggling to work it out.