The one on the Brattons web site says:
"New aircraft strength 1144 steel, with a Rockwell hardness of 23, and precision ground to within .0005 to meet Fords original specifications; polished for smooth surface. the best on the market. This is the Model 'B' cam. The 'B' cam creates twice as hot a spark as the 'A' cam, resulting in longer spark plug life."
What's the difference?