Gazelle? Does anyone know anything about them?

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.

What about brake drop? This ones is using Mafac Racers.

http://fivenineclimber.com/bikes/gazelle/my_dutch/my_champion_mondy1.htm

I'm assuming the A-Frame would be around 50ish?