I think this is my last peeve and after I air it I get to open my new Schaumburg Chrono, so I'm writing fast. Oh blessed world!
As far as I know it's only Ventura that consistently put 12 rather than 24 on the top of a GMT dial. I preferred that because it was the rising of the sun at 6 and the GMT hand swept upwards and then down to 18 at the close of day. After that the GMT hand half-circled the bottom part of darkness, a visual effect I enjoyed mimicking the cycle of rising sun to darkness, the nether lower world.