Since identified by Hardy Blechmann's book as an Air Force pattern ('Puzzle' pattern) introduced in the 1980's for use by ground crew and airfield defence personnel.
There is a secondhand/antique/military surplus store just a few minutes walk from where i live. If anyone are still interested in the pants i can check if he still has any left.
Many years ago a surplus catalog in the US (Sportsmans Guide) had "used" sets, top and bottom. I got a few sets and they turned out to be brand new and used. I was quite happy to replace my very used set I paid 3 times as much for a few years earlier
It is funny how often the shirts are seen without the trousers.