It is considered very lucky to find a key. Any sort of key is lucky, but an antique one is especially so. As with the finding of something red, there are words to say at the time of finding it:
The key to your heart lies on the ground.
The key to your heart has now been found.
I lock up your love with the heart of my own,
I’ll guard it forever with the love I have shown.
As you say these words, think of the one you love and of the two of you being together forever. Sleep with the key under your pillow for nine nights, carrying it with you during the day. It may then be put in a place of safety.