What does PTY (LTD) stand for?

PTY, usually used in conjunction with Ltd, thus (Pty) Ltd, stands for (Proprietary).

PTY representing "Proprietary" means private ownership.
This illustrates one of the main features of PTY LTD Companies:
that is, their shareholders are not publically declared, only their directors.
Thus the ownership is private.

What does "Ltd" stand for?
Ltd as used in the designation of a private or public company,
for example, either Bilkovo (Pty) Ltd or Bilkovo Ltd,
stands for "Limited"
and refers to the limitation on the liability of company shareholders and directors.