Death Mask
This is not an actual death mask but they are a real and really odd/interesting thing. Starting in the 1700s people would opt to memorialize themselves or a loved one after they died by placing a cast around their face (and later making it more permanent with metal/stone).
It sounds strange today, but considering that this was before photography and that painting was not accessible to everyone it’s understandable that people would use them to remember the face of someone they loved.