The easyest way to describe this is by an example:
A (norwegian) licence plate have five digits, lets say 12345 (the leftmost digit can not be zero, or so I'm told). Every each possible plate number can be represented by two symbols, called "numbols™".
There are 300 different symbols and that is sufficient to cover all plate numbers.
Numbols are basicly a nuber system. Just as we have number systems based on two (binary), ten (decimals), sixteen (hex), the Numbols system are based on 300.
The average human, and especially children, do not memorize licence plate numbers easily, nor do they do it fast, and in most cases: not at all.
Symbols of common and easy reccognizable objects on the other hand is easy, espacially when there is only two of them.
Due to the vast number of kidnapping, rape and killing committed in my country lately, where people and children was forced in to a vehicle. I got down to create this little system.
In the majority of those cases, the police asced if there where anyone witnessing suspicious cars.. Would you remember the licence plate number to a car sneaking around 5 days ago?
Perhaps there are other uses for this system too? Send your tip to me at mystefisten@gmail.com
Yes it can.
 Some of the symbols are too similar. This is just a quick demo. The symbols are arbitrary stuff taken from the web, to have something intermediately to work with.
The time it will take to create a proper set of symbols is just too mutch for a little hobby project. I do have a life appart from programming.

The symbols should be searchable by categories so that witnesses can more easily find the symbols they remember.

...
This is a challange
For now I suggest a sticker.. just as the sticker used to say what is your nationality
Many people will not be too happy about putting stickers on their cars, perhaps it should be voluntarily?
From plate number to symbol pair:
index of leftmost symbol: (N10000(N mod 300))/300 (alternate: ⌊N/300⌋) , where N = plate number
index of rightmost symbol: N mod 300
From symbols to plate number
N = A * 300¹ + B * 300º + 10000 , where A is the leftmost symbols index, B the rightmost, and N is the plate number