How to setup shaders for semitransparent mirrors? I would like to produce a box with an effect like this one : http://www.thisiscolossal.com/2015/07/guillaume-lachapelles-mirror-dioramas/  

I have been trying to create a mix shader between glossy and transparent to achieve this effect, but it didn't gave me anything close to this...  

Any ideas on what shader to use ?  

Thank you ! :)
This would be for the box containing the scene. 

With the geometry node backfacing information you can make an object that is transparent from the outside but glossy on the inside: