This is a vintage used Seiko pogue chrono case with a 6139-6022 caseback. This came out of a watchmaker's estate, I can't say whether the case and caseback go together or not. The case is 38.9mm across, 43.27mm from lug to lug and fits a 19mm band. As shown in the pics, this is dirty, scratched and scuffed up but the caseback has good threads and threads onto the case and fits as it should. This is sold as is.