This piece is a favorite! Its a mixed link paper clip chain. A classic with a twist. (note the paper clip link is 3/4" in length)
The chain is made up with a paper clip link, elongated oval link and round links. The pattern is consistent all the way around. The clasp is a nice size claw clasp. Metal = 14k yellow gold Chain thickness is 4.5 to 6 mm. A statement piece for sure. Wear alone or add your favorite charms. 
 
Total Length = 20"