Current papers use about 100 - 200 mg/sq ft.
Older papers used about 200-500 mg/sq ft. These are the so called silver rich emulsions of a byegone era. They are not superior in any sense, but rather suffer from a large number of grains that are dead. To approximate mg/sq meter multiply by 10 (actually about 9) to go from mg/sq ft to mg / sq meter.
My coatings use from 125 - 250 mg/sq ft, but I've gone as high as 500. It is merely another variation on a theme......
The dead grains come about by poor precipitation or poor chemical sensitization or both. Or, other factors which inhibit development such as Iodide at the wrong place at the wrong time in the wrong concentration.