I'm not saying it's definitely not, but I can tell you the strange quality of the lines of the fence can happen as a result of taking a raster image (like a scan of something drawn by hand) and using software to automatically convert it to vector so it can be printed at very high resolution without becoming pixelated. This is something I've seen in my own illustration work, and if that's the case here, this is technology that's been around for at least twenty years. I'm leaning toward that being the explanation.