I'm not sure if this should be in the category Boring Postcards or Inappropriate Postcards. It's not necessarily boring - the building itself is dull - but the photo shows some pleasant countryside surrounding it, even if it does suggest that the photographer popped up from behind the wall for the split second that it took to get the photo, before scooting off in case he'd been spotted by the guards.
I find myself asking who would buy this card and also who would send it? Would it be sent from an inmate? How delighted would you be to receive it? It's certainly not going to come with the ultimate postcard cliche, 'Having a lovly time wish you were here.'
There is an unused 3p stamp on the reverse which I think would have been the cost of first class postage around the mid 1970's. However there is no message so we can only guess as to who had intended to send it.