The pictures and description match what we americans call "mexican brick weed" pretty closely. We used to get a lot of jamaican like this too, but my understanding is that real jamaican is pretty rare now, it's almost all from mexico. In the 80's the east coast also got weed like this from belize, columbia, thailand and panama too, but i missed out on most that. Supposedly some the belize and panama coming in in the mid-80's was excellent. The potency of compresed imported weed can vary a lot. For people my age in the new york area, "ses/cess/sess" was the first weed most of us smoked. We used to buy it from rastas. I liked the way this weed would crumble easily. The smoke was a little harsh sometimes though. I always prefered the sativa high.
Now, everyone is obsessed with looks more than high, so i don't see this stuff around much. Everyone demands that weed have no seeds, not be compressed, not be brown, have "crystals," etc. So now we have lot's of imposter headies, some of which barely has any effect. The compressed weed we get now is greener, less dry and not as tightly packed into layers as sess was. It costs more too.