These use a parabola instead of a cone shape and so achieve a contact area four times greater than that of the spherical stylus. This improves tracking, reduces wear and doubles the stylus resonant frequency.
"Thank you for your outstanding service. The 78's of my wife's relatives you transferred to CD is phenominal. My wife found some old 78 rpm records of gospel songs recorded by her grandmother and other relatives. These 78's were the kind with a thin plastic coating over a metal disc. I would guess they were done in the 1930's. The coating had ..."