Antique long gold chain necklace sautoir rose gold early 1900's 60inches (7543)

Antique Arts & Crafts / Art Nouveau long chain necklace. Over 18k gold. Made late 19th to early 20th century. For origin, see Story below. 
 

Measurements:

Weight is 23.9 grams. Length, not including the loop approximately 58 3/4 inches 149cm. 

Description :

an extremely long gold chain. Very artistic in design, it straddles both the Art Nouveau and the Arts & Crafts era - late 1800's to early 1900's. Two shapes for links: long and round. The long links in mirror-image pairs. They each begin at a round base and then gold wires ballon out and intersect one another. They then intersect with their mirror image partner. Each pair of these long links is seperated by a trio of small, round links. The central link at right angles to the one that connects to the base of each of the longer links.  The system allows for full flexibility. 
The long chain or sautoir, as it is called in France is extremely versatile. It can be wound many times around the neck or worn as a belt or bracelet. There is no opening, but it would be very easy to add one. There are two larger loops attached (one of which could form a clasp, if so desired) intended to attach a charm or other jewel. 

Marks and Metal:

 Hallmarks on one of the loops near the attached larger clasp. Possibly French horse and eagle heads and lozenge for maker's mark. Gold was electronically tested as 19.2k - above 18k gold.
     

Condition:

Good with negligible wear commensurate with age.  Please see enlarged pictures and don't hesitate to ask questions which we will do our best to answer.   

THE STORY:

Sautoirs like this are fantastically versatile. They add the perfect finishing touch to any outfit. Today, they have become very unisex as men as well as women are increasingly wearing them. 
Long sautoirs are almost synonymous with fabulous Art Nouveau jewelry in France. They were very popular, probably because they are so attractive and versatile. Today, original, long sautoirs are becoming increasingly rare and highly sought after as many were broken down to form smaller items or lost altogether. 
We have a small mystery about the origin of this particular sautoir.  I bought it in Paris, where the seller told me that the hallmarks on the chain are the eagle and horse head (French marks for 18k gold) as well as the maker's mark lozenge. While the marks are clearly there, they are not clear to me. Furthermore, the gold tested as 19.2k, which is usually Portuguese. Was this a French sautoir made to a higher standard, or was it made in Portugal and then bought in Paris where it lived for the last 125 years or so?