Gazelle? Does anyone know anything about them?

Is there any difference in geometry (chainstays, angles etc) between the A-frame and the AB? Also I've seen some with band on down tube levers and some with braze on gear bosses. Was this to do with the year?

Same geometry.
Just different dropouts, fork crown and some braze-ons.
A-frame has long dropouts with eyelets, AB short fropouts without eyelets.
Whole geometry incl chain stay length is the same.
During the years, the front forks and height of brake bridge have been changed to accomodate piccolo brakes.