I believe Joesph Asscher designed the asscher cut in 1902. It was designed to enhance the brilliance of the emerald cut. Unlike the emerald cut, the asscher has a smaller table and bigger step facets. The asscher has more fire though than the emerald cut and a deeper pavilion. The Royal Asscher has 74 facets. It has wider corners and more pavilion step facets to make it sparkle more and add more brilliance.
Here is a diagram of the difference of the Royal Asscher (top) and the Asscher (bottom)
Good to see another Esscher fan coming out of the shade. I wonder what would have come if some of his perspective charades would inform diamond cutters! Although, asscher diamonds are also loved for the false perspective inside them, don't they.