vacation with pay stamps

Maybe someone can tell me how these worked. I've seen them in the Van Dam catalogue, but these are the first I've come across. Picked up this book today. A 1957 Vacation With Pay Stamp Book. Inside are five stamps of different denomination. The book looks almost new, but considering these are the only stamps in it, I guess the 'employee' didn't use it very long.
Anyone know how this system worked? From what I can gather, the stamps acted as a sort of credit.