Men's Heako Obi, Dark Navy, Shibori

This is a men's heko obi (a type of sash). It still has its original stitching and is unused, but it has been stored in a chest for many years, so it has noticeable wrinkles. I apologize for my lack of expertise, but based on the feel, I don't believe it is made of pure silk.
Thank you for looking.