rich, dark brown velvet band collar, with silver rococo-style scroll connectors at either end, and a black satin ribbon that laces between them.    

there is no clasp or anything in the back. 
You have to just loosen or undo the ribbon to get it over your head.  
Be prepared to spend a couple minutes getting this on and off.  about 11.5" fully closed.   
it looks best with a little gap, so i'd say best fit for someone with a neck between 11.5 to maybe 13" around, but can go larger. 
there's quite a bit of extra ribbon for thicker necks.   

Lots of other necklaces, including this in other colors, available in my ebay store.