Vintage or vintage styled CR's are all relatively long-ish jackets. If you're going for the Brooks kinda deal, I'm not sure you will find one that won't cover your belt.
I was kinda kicking that thought around. I may be ordering a new CR from the new Hercules outfit and if I ordered a length of 23" it would be just above my belt. But I don't want to screw it up.. . So I will probably play conservative and order 25". I don't think I could pull off the belt showing anyway. It looks cool, but probably age-inappropriate for me. Thank you all responders, particularly Carlos840, for very useful information.
I prefer the jacket to sit on the belt, definitely not below, however that leaves the back a little short and draughty when riding if its a straight rear hem, I tend to go jackets with a rear 'drop', shirttail hem and on a recent bespoke riding jacket I had a drop added and both front and bsck are perfect. Some of the makers, particularly the Japanese brands have jackets where the sizing looks great on Instagram but in reality would be incredibly impractical for daily wear with hems way above the belt and sleeves sitting above the wrist, it makes for a cool picture but bending over or raising your arms when driving or riding would be awkward as hell. Some of these jackets are on models with the chest and biceps of a 13 year old kid.