At first glance you may think this cover has
an automated slogan.
http://cjoint.com/data/fihH7CJaST.htm
341Kb
I suggest it attracts the definition "auxilliary marking"
I reckon it's travelled through the automated canceller,
the stamp has been cancelled, but the cover diverted to
a default bin, for unrecognised destination.
After physical observance the cover has been re routed
in the appropriate queue, where the top impression
has been printed.
It appears we are to draw our own little squares
for our postcodes when addressing non approved
post office packaging
but all this is only a guess.
