These was issued to troops serving in Northern Ireland. Of US manufacture, the first ones issued came with zips. The main drawback with zips being the disastrous consequences for the wearer when hit by a petrol bomb, as this would melt the zip.
Later models came with velcro fastening and rubber shoulder stops to facilitate easier aiming of the Rubber Dick Gun and SLR. A good advantage of the flak jacket over CBA was it could be easily removed and put on over your combat jacket. And it made a good pillow to rest your weary head on too.