American individualist anarchist Josiah Warren, who embraced the labor theory of value, which says that the value of a commodity is the amount of labor that goes into producing or acquiring it. From this he concluded that it was therefore unethical to charge more labor for a product than the labor required to produce it.
The Cincinnati Time Store was a successful retail store, created by Josiah Warren. In the store, customers could purchase goods with "labor notes" which represented an agreement to perform labor. After a rough initial period, the store proved to be very successful. Warren's goods were much cheaper than competitors', though he maintained that he was not trying to put other stores out of business.
Though the store was successful, the problem of equal labor times for different difficulties of work was a concern for Warren.
Even in the 21th century, Cincinnati Time Store is an interesting project. It inspired Julieta Aranda and Anton Vidokle for their project project Time Bank. Time Bank (2009) is a world wide group of people who create an alternative economy by changing time and skills.