Not sure what module your watch or clock gear is? This chart was made for exactly that.
Watch and clock gears are cycloidal — a tooth form designed for low friction and high precision in fine mechanisms, quite different from the involute gears found in motors and machines. Without the right reference, identifying them is guesswork.
The Evolvent Cycloidal Gear Module Identification Chart shows actual-size tooth profiles for both gear wheels and pinion leaves across 19 modules, from the finest watchmaking sizes all the way up to larger clock work:
0.10 · 0.12 · 0.15 · 0.20 · 0.25 · 0.30 · 0.40 · 0.50 · 0.60 · 0.80 · 1.00 · 1.25 · 1.50 · 1.75 · 2.00 · 2.25 · 2.50 · 2.75 · 3.00
Just hold your gear up to the chart, find the matching profile, and read off the module. Identification formulas are also printed on the chart for calculating module from outside diameter and tooth count.