I think it is a tool to mark the point end of a dart to shape the bust area of a blouse or dress. If those opaque things are chalk, it is even more likely.
I don't remember how to do it, but there is a google image search that you can do.
I love theses "what is it topics."
Yes this is what it is. I have this. The point goes into the middle of the chalk with fabric in between. Twist the handles to mark the fabric. It will do both sides .