I find myself over and over returning to Victorian-inspired mourning jewelry. I'm not a goth or steampunk gal, it's just something about the somber mood of these pieces by Mata Hari Jewelry that I find enticing and appropriate.
I imagine this tiny heart and key charm as a piece that could given as a gift to comfort someone who's in mourning. Keep the heart, but place the key close to the one recently lost. If they are to be buried, then the key could be placed in their hand or in a pocket. If the loved one has been cremated, the key could be placed in the ashes. Someday the two will be reunited.