2 cent:
I agree with previous posters that I have not seen a pair of pinking shears with a zig-zag any finer than the typical "pinking" cut.
Having a lazy Friday evening, I wondered "what is the gauge of a pair of pinking shears?" (Never asked THAT question before!) I contacted an avid sewing friend who owns 3 pairs, all essentially identical (and who has never seen a different zig-zag rate). I borrowed 1 pair of Wiss shears, total length of 9 inches.

Made a cut in a piece of pink construction paper, which when placed along the centimeter rule of a Phil-A-Meter shows slightly more than 4 peaks in 2cm.

Using the sliding scale of a Multi-Gauge, every 3rd point aligns very well with 12.3, which comes to a more exact "perf 4.1" (illustration not included here).
Making 3 staggered overlapping cuts results in a simulated perf 12.3! Here set against a perf 12 stamp to give a fairly close match.

While this may not be how the left side was modified, it does make a close reproduction. Now back to your regularly scheduled program!