What can a PAO system encode?

Any fixed set of items — most commonly the 52 playing cards, or the 100 numbers 00–99.

* A completed 00–99 number-peg grid — one fixed image locked to every value. — Pedros.lol, CC BY-SA 4.0, via Wikimedia Commons. *

The two classic uses:

• Cards — a PAO for all 52 cards powers deck memorisation.
• Numbers — a PAO for 00–99 lets you swallow 6 digits per image (a 2-digit Person + 2-digit Action + 2-digit Object).

Anything with a fixed, finite item set can get a PAO. The upfront cost is building and drilling the system; the payoff is dense, fast encoding forever after.

Go deeper:

• Mnemonic major system (Wikipedia) — how digits become the sounds behind a numeric PAO.
• Numeric PAO example (Wikipedia) — the 00–99 person/action/object example.