Code Currency - A type of non-material currency based upon a code

Hypothetical situation:

X works in a shop, she is given a code by her employer.
"If someone presents you with this code", he says, "They are entitled to take 5 items worth value Z. After they give you the code then it can't be used again by anyone else".
Someone does a job for the employer. He pays that person by telling them the code.
They go to the shop and give the code to X and recieve the 5 items worth value Z.

 

Note: I am not suggesting that this form of currency could be used on a large scale but it could be used in odd circumstances where other forms of currency aren't available.