I also bought a "Buffalo" top from a fleabay army surplus seller. It does appear to be ex UK army but made in China, is a similar design but shorter zips on vents and chest pocket, and a similar fleece to the Active Lite shirt. I hoped to use and abuse the surplus one keeping the Lite shirt in better nick, the Slate colour is nicer than the Buffalo black or green. But the surplus thing is really sweaty, even has zippits too. The outer looks and feels pertexy but it's flipping horrible. There's a jacket from the same place, same thing, bought for the Mrs for gardening who can't do pullover tops for some reason, but being a Lady doesn't sweat so less of an issue
It's label says SMOCK, LIGHTWEIGHT, THERMAL, (PCS), Light Olive NSN 8415-99-813-3292, about £35 wasted.
Or anything underneath it! They are the most clingy garment ever lolThat's not a Buffalo, that's the Brit Army issue top. Fleece on the inside instead of pile. A nice top on it's own but not a Buffalo, as you have found. And you try putting it on/taking it off when you have a fleece on!