Help to ID French Pocket Watch painting

GILLION A PARIS ENAMEL QUARTER REPEATER POCKET WATCH

hallmark is 1819-1838 non-paris

The biggest mystery is the painting, the specific definition of "enamel", which is fired on 800 C degree, and it will be a colorful glass,

but this is not, if it is the "enamel" which usually talking about on watch, it would not be afraid of any hot needles, but this paining is.


The seller told me that this is another type of enamel, but I can't find any information, or another pocket watch is like this one,

The most similar art I found that was "miniature painting", but In the 19 century, it painted the human face on ivory mostly,

I couldn't find any example on pocket watches neither.

So it weak my confidence about the painting. was painted in the modern? in the nearly 100 years? in the 19 century?

Why painting it? Who painting it? Maybe they are being question forever...