I have inadvertently invented a ternary tallying number system.
Our drinks fridge at work sells cans of soft-drink for $1.50 and small chocolates for $0.50. One day I didn't have change, so I wrote my name on a sticky-note and put a vertical stroke beside it – signifying one drink.
Then, at another time, I wanted a drink and a chocolate, so I drew a short stroke beside another regular-sized one. Thus the tally read: two big items, one small.
Then I wanted another chocolate but didn't have change, so I added a small stroke above the existing one, with a gap between. Thus two small items beside my two big ones.
The revelation came when I wanted a third chocolate. It occurred to me that three chocolates is the same price as a single drink, so I simply filled the gap between the small strokes. And so my ternary tallying number system was born.
2 = ¦
3 = |
There is ambiguity, of course, because there's no distinction between an isolated 1 and 3, however since there's never more than a single 1-digit in the tally, the ambiguity is quickly resolved.
You could include a parity mark if you wanted to indicate the height of a 3-digit; or similarly you could add something to the 3-digit (for example a small slash: ∤ ), but personally I can't be bothered.