There was an early style of rear brake roller for canti's which later changed to a rocker style setup. I think production moved to taiwan around '96, from what I hear the taiwanese frames crack less.
To all interested in the cracking issue on the frame around the rocker pivot mount.
When I took mine apart I found that the lugs on the frame which hold the rocker were being deformed considerably when the bolt was tightened. I made some top hat washers of a more suitable size to fill the gap which stop the lugs having to bend. I think this poor fabrication is likely to be the root cause of cracks in this area.