Give it another look.

This dull brown and gray clock. Doesn't work. Useless. But why is it so heavy then? Inga felt a spark go off in her mind. Surely, it hides a secret. It has to. The glass above the still hands would not give, so she decided to look elsewhere before trying to force her way in from there.

Indeed, another lid in the lower part, pretending to be a part of the ornament. No catches or buttons, so it must be a push lid. After leaving a lot of fingerprints, pressing both upper corners with force did the trick, and the lid pushed inwards, releasing three different old-fashioned keys.

With no heirloom chests in sight, Inga held onto the celebratory feeling of discovery itself before putting the clock down along with the keys. If she happened to need them, they would be right there. It's not like this place was full of key thieves anyway.