Actually, there's more to these little blighters, every schoolboy packet from the 60's was full of them. They are official reprints aimed solidly at the collectors market. They were printed CTO, without gum, in 1957, & all of the 5-Year-Plan issues were covered (I think it's a total of 51 stamps, but don't quote me on that one).
Telling them apart from the 1st issues is easy, it's the position of the last 'E' in 'DEUTSCHE'.
In the 1st issue the 'E' is mostly above the 'T' of DEMOKRATISCHE'.
In the reprint the 'E' is above the 'A' of DEMOKRATISCHE'.

1st issue left, reprint right. (From the Michel German Specialised Catalogue)
All the reprints are cataloged at minimum handling charge, but the real value would be something like 50cents/hundred