Opening the points causes the spark. The coil hot wire is on the positive terminal of the coil. The movable point is connected to both the coil negative terminal and the positive of the cap/condenser. The fixed point and negative (case) of the condenser are grounded/negative.

Having adjusted the timing on a few - I can state with some certainty that there is an ignition type that fires when the points close.

 

Opening the points causes the spark. The coil hot wire is on the positive terminal of the coil. The movable point is connected to both the coil negative terminal and the positive of the cap/condenser. The fixed point and negative (case) of the condenser are grounded/negative.

The one's I've encountered on older mopeds, spark on points closing.

The IGN generator is aligned for maximum amplitude at the firing point, and the points short the primary at maximum magnetic flux - that energy has to go somewhere.

 

I was talking about a cars ignition, since I stated "battery". On an magneto ignition I've ever seen/worked on it sparks on points opening. Not saying the other type doesn't exist, just never seen one.