An excellent reproduction of saving stamps for KdF-Wagen Savings Booklet (KdF-Wagen Sparkarte). There are 3 variants available
5RM: red (1938-41) or green (1942-45) - to cover mandatory cost of car and insurance
4RM: purple - to cover optional costs of extras (i.e. convertible) and transportation
The 5RM stamps can be bought as a strip of 10 or as a whole block of 50. It happened frequently that the whole block was purchased at once (for RM 250) by wealthier individuals and pasted into a booklet after being cut in 2 halves) rendering boklet complete (5 booklets were needed for the car)
 
Originals had tiny, almost invisible DAF watermark and were embossed. These features are not reproduced. 
 
History:
One could get the car by subscribing at Kraft durch Freude (KdF) and prepaying / saving at least RM.5 a week. For each RM.5 you would get a stamp for the savings booklet. 5 booklets later, the car was yours and you could hit the Autobahn!
It started in 1938 as a noble Führer's idea to allow any German worker to own a car. Hitler set a cost limit to 1000 RM (around 5 monthly salaries of qualified factory worker) and Ferdinand Porsche design it to fit in this budget. To learn more about the history, check my dedicated blog post.