Mines dated 1990 OG and has a removable frame.
I'd be interested to see the differences in design. I have seen one that had a QR buckle on the shoulder so you could drop the pack like an ALICE pack.
i got it off the bay for a tenner i think some time ago, it had just been listed as a green army rucksack! has one name on the name label which is white cloth. virtually un used by the look of it, came with one side pouch which was darker and really really stiff and stays in shape even when empty. all zips are identical plce type and everything is the same as a later one, no qr buckles on the straps though?
the frame is a two prong version which i don't like as much as the three prong, doesn't feel as stable around the top of the straps. the only other thing i noticed was that though the buckles for adjusting the shoulder straps are same shape and type, you can't just pull the leader to tightenen them up while youve got it on, you have to lift it slightly as you do for loosening off the strap. it's like the teeth are biting in both directions on the webbing, but this may be due to lack of use in it's previous life. also the straps are unfinished and just heat sealed so you can unthread them from the buckles very easily.
the velcro closed flap inside the bag that covers the head of the frame on my later ones is not present and the very top of the frame is visible showing the rivets to the main bag. was surprised to see this as replacement of frame is not possible without destroying the bag, probably why it was changed. all the stamps are immaculate and show the date 1989 and rucksack, convoluted, long etc.
bit of a find and if another og bergen comes my way i might get it just so i don't over use what could be a collectable down the line.
cheers all
Rob