The Garden Gnomes

What an excellent choice! You're halfway through an exciting game of (improvised) Quidditch when you notice a glimmer out of the corner of your eye. You fly over to where you just saw a flash of gold to notice not the snitch, but a small coin in the grass. Your eyebrows shoot up in surprise when you find another one and another one... There's actually an entire trail of golden coins and you have to suppress a scream when you see what the trail leads to. You call out for your friends and they fly over to you immediately. "What is that thing?" you ask Leonora and she chuckles. "That would be our garden gnomes, ugly things aren't they?" You ask her what they're doing and if they are dangerous in any way. Leonora answers that they have always been there and that they're not dangerous but they are mean biters. You're about to fly away when you notice that one of the gnomes is holding something, it appears to be made of wood. "What's that?" you ask your friends.

Upon closer inspection, you can make out a small wooden chest. You all dismount your brooms to get closer to the garden gnome who is carrying the object. "Hey, that belongs to my grandmother!" Leonora shouts at the gnome who starts making a run for it. You all manage to catch the gnome and take the chest from him, but not without a few bite marks. "What's in it?" one of you asks. "I don't know," Leonora says while she is studying the wooden chest. "Should we open it?" Your curiosity gets the best of you. "I would, but it's locked and we can't use magic outside of school," Leonora says, sounding disappointed. You take another close look at the chest to find that it has a muggle lock on it asking for a three-digit code. Maybe the gnomes have also stolen the code?