To avoid counterfeits chips and jetons were sometimes double numbered.

I just listed two new Compagnie Generale Transatlantique mother of pearl chips.
The difference for the 100 F is quite obvious, it’s an octangle. The one on the guide is round.

The difference for the 20 F chip is something more subtle.
The 2 is different and the symbol below the F is a rectangle.

Here are the numbers, the first numbers are the serial numbers.
I took the liberty to use the numbers of the chipguide also.
91 – 226
300 – 809
366 – 1007 (chipguide)
886 – 1160
900 – 1116

The first one to find the formula get's a nice chip for free.

Enjoy your sunday.
Jo