I've learned a lot from your comments and done some research of my own. The lights (two out of three) may possibly be original to our old brick row house, but they are definitely of the era. Upon closer examination, two of the three lights are IDENTICAL. How did we not notice before?!
The style is called a 'pan light' and the lights are called 'drops' so, our lights are 'five drop pan lights.' I still don't know what they're made of, but apparently, if they are super heavy like ours, they could be made of 'pot metal,' which is zinc and brass with some kind of applied finish. I also learned that the 'cup' things on the bottom of the lights (see image below) can be screwed off. I was so hopeful when I screwed it off because I figured that maybe I could screw a nice glass shade back on, but alas, I can't locate any shades with a one and three-eights inch opening. The smallest shade opening I can find is 2 1/4
And also? Holy cow They might be valuable. A similar light sold online recently for $600. That could buy a lot of mulch and flowers for the backyard things we really need.
I'm still not sure what we'll do with our pan lights, but I promise to keep you updated.