I am a fan of pure object systems for their simplicity and versatility in memorizing strings of digits of different length, such as addresses, phone numbers, etc. You can do that stuff with PAO also, but PAO takes more work and is not necessary. When using a 2-digit system, which is what you need for your purposes, PAO might allow for quicker memorization of digits in the short run. But it doesn’t look like you’ll be racing anyone, so making a PAO list might be overkill for you. Instead, just make 100 objects that are unique and somewhat interesting for all 2 digit numbers 00-99. By “interesting” I mean it should have mobile parts or a specific function. A stick is an okay object, but a slingshot is probably better. You don’t have to rack your brains trying to find the perfect objects, but unique, wacky, colorful, mobile, meaningful/sentimental images will usually be easier to remember and easier to make interact with the other objects.