It is 8" long, but when clasped it is 7.5" long.Marked with makers mark, Made in Switzerland, Plaque ORL, and 20 Microns. 1 micron and up is good quality plating.
For instance, flash plating is less than 1 micron.
May be from the 40s up the 60s.
Has three rows of Panther links, and hidden clasp which is another good sign of quality.
Very fine quality.