Mint M31 tropical bread bag 'RBNr 0/0850/084 45'

Here we have an unissued, stone mint tropical model of the M31 bread bag. 
 
It is marked with the 'RBNr 0/0850/084' maker code, along with a '45' stamp for the year (?) or an assembly marking. 
 
This example is complete with all of the loops and buttons, as well as the full length internal closure straps made from a beige coloured rayon type material. 
 
This is the only the second example of this particular variant of bread bag which we have ever seen to date!