Not every box she found was a treasure box. And some of the boxes she found became treasure boxes.
One of her favorite boxes was one she'd been carrying around for a few years. She'd originally stored some treasures in it, but a chink in the box had allowed spiders and creepy-crawlies to infest it. She hated spiders. When she first discovered the infestation, she snapped the lid shut and shoved the box into a deep, dark corner, vowing to never touch it again. And for a long time, she didn't.
But she did really like that box. It was the kind that fit in her arms without being too bulky or unwieldy, and it didn't take too much effort to haul it around. So eventually, she decided to be brave enough to crack the lid and look inside.
Most of the nasties had died. It was kind of gross, but much more manageable than living, crawling things. She started cleaning it out carefully, clearing out the debris and wiping away the cobwebs. Before long, the box was glistening and clean again, the original keepsakes revealed once more. Finally, she poked around the outside of the box until she found the chink. It was small, and she meticulously filled it in, ensuring that the box couldn't be re-infested.
It was nice to be able to use that box again.
It became its own treasure box, of sorts. While she didn't place her most valuable treasures in the box, it became home to many keepsakes and small things that she was very fond of.
One day, she came home from work and considered the box where it sat in unobtrusive but fairly prominent place in her living room. It really was becoming a valuable and well-loved treasure box. It might be worth it to put some things of greater value in it.
She put a hand on her pocket. The now-familiar and surprisingly comforting weight of the key in her pocket kept her company everywhere she went. A constant reminder of the promise her father had made.
Maybe...
But the box had no lock on it. It was one of her most prized possessions, true. But the key needed a lock. Her best, most private treasures were stored in the box her father had mentioned. She knew all the contents of the box in front of her, and most of them were smaller and simpler than the wonderful things she'd placed in the treasure box that her father had cleaned out.
Kneeling beside the patched-up, well-polished box, she opened it and sifted through the contents, trailing her fingers lovingly over the various pieces of her life that she'd placed in it. There was room in the box for treasures of greater value. Maybe it was time to add something bigger to the collection in the box.
Or, perhaps, she could clean it out and give it to someone else...