These series of 4 stamps was issued on 28th of October 1940 to commemorate the first anniversary of establishing the General Government (administrative unit ruling occupied Poland) and to collect money to help poor German families survive winter (Winterhilfswerk, WHW). 
 
The stamps come in 4 different colors/denomination:
green - 12+8 = 20gr (nominal stamp value of 12gr plus 8gr donation to WHW)
red - 24+16 = 40gr
brown - 30+ 30 = 60gr
blue - 50 + 50 = 1zł
 
You can receive the following configurations of these stamps:
a strip of 5 identical stamps (green, brown, red or blue)
a strip of 4 stamps (one of each) 
 
These beautiful stamps were designed by a German painter and artist Otto Engelhardt-Kyffhäuser. He was an SA, SS and NSDAP member, which certainly helped him get some business.