Thanks for that link, chiz.
The brochure says:
The 155LC stylus is a "modified Shibata stylus precision-ground to a linear contact tip shape".
The 140LC stylus is a "linear contact stylus resulting from further refinement of the Shibata stylus"
I remember reading (maybe in this thread) that the Shibata stylus has a curved contact patch. So maybe the AT stylus is a modification to remove that curvature. (?)
None of the drawings showing Shibata contact patches seem to show this curvature, however.
I also noted that the top cartridge described in that AT brochure is the AT1000 (MC), which has an "ultra-low mass (0.006 mg) 0.06 mm square shank natural diamond ground to an elliptical cross section and nude-mounted to a natural diamond, taper-cut cantilever. Moving mass is extremely low, and signal transfer speed is higher than that of any cartridge manufactured today."
Perhaps it's logical to assume the 155LC stylus weighs around four times as much as the AT1000 stylus, or around 0.024 mg. But we don't know how long these diamonds are, do we?