The Omega reference 176.0012 Mark IV was introduced in 1973 and ended production in 1974 - a short run to say the least comes on old school Omega bracelet which I understand is not common to find with these but then again I'm not an expert. I've had it on a few different options that work pretty well - pictures below  the Mark IV is built around the Lemania 1340 (AKA Omega c.1040) automatic movement, which features a central minute counter hand (not to be confused with the later 4.5 which ditches the central minute counter for a traditional minute counter subdial) an hour totalizer at 6 and a very cool combination running seconds and AM/PM display at 9 Chrono is snappy to operate and zero's perfectly  Tourneau case is 41.4 diameter and 45 hooded lug to hooded lug Case is lightly touched up - beautiful sunburst brushing on top and horizontal brushing on the sides and a crisp polished section to separate Baton markers have patinad to a wonderful light khaki and is a perfect compliment to the black dial and white hands service history unknown but I haven't had any problems  what you should know:  bracelet has a little stretch - not much - but hey, it's 50 yrs old. crystal, again, 50 years old, is not perfect - very small chips on the very outer edge of the crystal at 11 and 3 - 1) you're not taking this in the water anyway and 2) probably wouldn't notice unless you are looking for them watch and bracelet only  Asking $2500 on the old school Omega bracelet Or Best Offer