19mm diameter only - Tiny Antique Pocket Watch decorated with Diamonds

Tiny pocket watch from circa 1860s.

It's one of the smallest pocket watches ever made.
In fact, it's too small to be worn in pocket and more suitable to be attached as pendant. Diameter is less than 20mm, height without bow is 26mm, weight is 8,5 grams.
Very rare size, probably only 8 lines calibre.
Jaquet & Chapuis in the book "History of the Swiss Watch" shows similar sized watch.

Watch is decorated with beautiful blue enamel over guilloche background and diamonds of old rose cut.

The dust cover signed by Perret & Cie in Geneve.
O. Patrizzi mentions "PERRET Eugenio & Cie", middle of XIX century, specialists in pendant watches and watches with lever escapement.
The case is Swiss made and bears 18k French import hallmark.




Condition
The watch appears to be in good condition.
The movement works, but I don't guarantee time keeping.
Dial seems to be free from defects.
Case has minor wear, enamel is intact
Mineral crystal, original hands.