Up for sale is a NOS Omega caseback reference 112ST1139. I believe it should technically fit every speedmaster professional except the 3861. It comes as pictured still sealed in the original packaging from Omega. Please study the photos, as they are so much appreciated it aww a key part of the description, and feel free to reach out with any questions or concerns. I am happy to take more photos upon request and answer question. As I reduce the size of my eBay store and sell off some inventory, all my watches and watch parts are being offered with no returns, so please reach out if you have any concerns and ensure that this suits your needs. I really appreciate your purchase and support! Thank you for checking out my store!