Huge is a good descriptor. There are 10,000 #6's for every #7 and so on and so on. This will cover 16X20! Perhaps it would just cover Mammoth plate, I don't know. The reason there are so few is that 1,000 people needed a #6 in 1880 for every one that needed this size. Yes, I'm making these numbers up, but prove me wrong. I've owned at least 4 #6's in my span, but this is the only #7 I've ever seen. They made a #8 also. Special order?? This is in stunning condition as the photos show. The price is steep. I hope I keep it. I will sell it for $1325. I am re-investing my $$$ in these days. But it's a fine investment, and if I keep it, that will please me also.