It's one of these: https://www.ottosantiques.com/products/early-20th-century-drawing-board-by-simplon
And most of the stars that are in that circle are invisible to the naked eye because they’re red or brown dwarfs and not bright enough. For that reason we can’t even see our nearest neighbour Proxima Centuri, which is only 4.2 light years away. And although the night sky seems to be teeming with stars, even with perfect viewing conditions and good visual acuity, there are only c.9,000 stars visible to the naked eye, total (so half that number per hemisphere).
I'm not entirely sure that circle is only what we can see from earth because the photograph would have to be taken from outside our own galaxy. Or am I looking at this too literally and this is an example of the area we could see in our own galaxy. But this also wouldn't be literally correct either because we can see thousands of galaxies from earth each of which contains billions of stars. Pedants corner... moi?
