This is a Seiko Lord Marvel, ref. 5740-0010. It's a later model in the Lord Marvel series, which ran for about 20 years, and features a movement based on the Crown. This is a famous movement with fine adjustment and hacking functions. The movement was later modified from 5Hz to 10Hz, resulting in the well-known Lord Marvel 36000. I don't have a screw back opener, so I don't have pictures of the inside, but since it's a 5Hz model, the movement is likely a 5740A. The dial has a beautiful silver sunray finish. There are minor scratches from use, and a slightly larger dent on the case side (photo 3), but the seahorse emblem on the back cover is still clear, so I think the condition is not bad. It is, of course, a working watch, but it has a daily rate of about -60 seconds when laid flat, so please consider an overhaul if you are concerned.