Ohhhh, Corsetiere!!! I am so jealous, and I am proud to say it!
Those covers are so beautiful! Lucky you!! I can't wait to see what they will look like once you put something on them to bring out the detail.
JacquieJet, back in the day that these were used, chimneys didn't have dampers. That meant the heat went out the chimney in the winter and winds and such would blow trash into the room when the fireplace wasn't in use. They are a lovely alternative to shoving old newspaper into the top of the fireplace to cut the drafts out. In my house, I have the newspaper method because I haven't been as fortunate as Corsetiere.
As for the lead paint, I used to eat paint chips as a kid off my grandparents' porch door. Tasted like almonds. I'm still here!