In my personal canon, my character, Claire Greene, had previously worked in law enforcement throughout her 20's, eventually serving on Boston's SWAT team, a career she ended after being seriously injured in a shootout with Eddie Winters' gang (this is my retcon for her ability to use weapons and power armor so effectively).

She later settled into a more modest life as a mother and aspiring lawyer, but her hunger for action never died, and although she looked back on her service with a reluctant pride, since times were getting increasingly violent, she kept this beret as a prized possession, hastily grabbing it from her home moments before Boston fell to nuclear fire, and she escaped to Vault 111.

"Do you ever take that beret off?" ~Gwyneth Holmes