The way it was explained to me when I owned a Rolleiflex 2.8 F Planar, was like this.

Lens Name---------------------# of lens elements

Schneider Xenar---------------3 elements,
Zeiss Tessar-------------------4 elements, a symmetrical lens design,
Schneider Xenotar-------------5 elements,
Zeiss Planar--------------------6 elements.

None of these are T*, or HFT coated.