These are a true French Vintage 'coup de coeur' 

A set of 12 porte-couteux or knife rests from the Art Deco period.  They are a little chippy, but still perfectly useable,  from a life spanning nearly 90 years, the colour of the glass is a little green which may not show in the photos and there are charming random bubbles in the glass. 
It is considered impolite to rest your knife on your plate and a dreadful thing to get the linen tablecloth dirty, so the solution for an elegant meal is to use kniferests. 

Art Deco set of 12 knife rests