Any reference from the ultra rare 2915 to the uncommon but much more easily located 145.012 As an aside, my observation is that pretty much every cal. 321 speedmaster ebay auction that goes to completion ends up with about 1,000 views which is about twice the number of views nice connies typically generate. Also the cal. 321 speedies usually have 100-150 auction watchers which again is a nice high number. Just a testament to how known and sought after these watches are.