58 pattern. First experience was Dartmoor, POC troop.
6ft 3 recently arrived from Africa. Issued a smelly lumpy paper thin green plasticy thing designed for a bloody dwarf.
How happy was I lieing there under the stars, sort of, rain obscured my vision, in a nasty bag that came up to my arm pits with a stuck zip and little velcro bits that had long since curled up and died. To top it off charged a 5iver when I handed it back in as apparently it was stained/torn.
The new sleep system

was a major step ahead. Even better when a wider mouthed bivvy was provided. The first ones meant having to pull the bag nearly out of the goretex to get in or out. Smashing for morale in the wet welsh wilds. Of course it meant that you couldnt actually pack much else and tieing it to the top of ones large pack was a little cumbersome.
And what was tolerably cozy in Germany was like a sauna in Angola and bloody freezing in Norway. Happy days eh.