Type XX Bezel

All three brands utilize 12-hour bi-directional count-up bezels, with numerals in black paint. The “6” and “9” numerals are “open” in style.

Mathey-Tissot
The 12 o’clock triangle appears in both black and yellow, though I believe black to be original to the watch.

Girard-Perregaux
The 12 o’clock triangle appears in both black and yellow, and varying on enough examples (with both colors on both dial styles) that it seems likely that the triangles may have been black or yellow originally.

Breguet
The 12 o’clock triangle is seen far more often in black, though some examples are yellow.

There are two examples known with different bezel types with numerals, and one additional with no numerals:
1. Countdown from 55 to 0. This watch also features a tachymetre dial.
2. Count-up from 0 to 60.
3. No numerals, dots only for each hour, including where at the 12 o’clock position.

I do not believe any of these three to be original.