I have been very lucky to source these beautiful high quaolity cache clous in Paris.
 
They are absolutely huge compared to normal cache clous (meaning literally hide the nail) They were pit over the nail, from which the picture was suspended on a cord or chain.  There is a tube on the reverse which pops over the nail.
 
The design is intricate, can you see the little acorns and oak leaves? One of the key symbols of Northern half of France.  They are and well cast, of thick metal with the original gilding and of the best quality. 
 
They measure an amazing 4" by 4" The tealight goves you an indication of the size