They were developed in Germany in the 1970s (I'm not sure of the definition of heritage breed for chickens...I know for turkeys it is natural breeding). Like with all breeds there is varying quality being produced. A couple of defects people have noted in less quality birds are white earlobes...
I recently purchased eggs from a gentleman in Illinois...they are in the incubator so I can't vouch for the quality, but he says he's been working to breed correct Biels. If he's close enough, might be worth a shot.