Can Someone Please Explain Me The Difference?!

Hello again,
Can someone please explain to me whats the difference between original stamp and overprint stamp? (the stamp with the 5 number)
As you can see, in this catalogue - signed stamps value is higher than unsigned stamps. I have the whole set overprinted and signed.
Can someone pls tell me if it's worth something ?
Thanks guys :)

Sorry - this is Germany Demokratik stamp! year: 1956 :)

Let me take a stab at your question. It's a question of watermark (Wasserzeichen) and type of paper. The pricey stamps on the upper left page (Michel Numbers 29-33) are for mint not hinged (two asterisks). They are identical to Michel Numbers 18-28 except they are on granite (gefasertes) paper.

Granite Paper



They have watermark 2.The 1957 issues below them (34-41) are also on granite paper but have a different watermark, a number 3.

DDR Watermarks


The 1956 issues on the right are a different series, "Dienstmarken B" the other ones are "Dienstmarken A" The pricy ones there are for used (circle with a dot) or on cover (The little envelope). Most used issues encountered are CTO, Cancelled to order (filled circle). The only good way to differentiate between a CTO and a real used stamp is to have it examined by an expert.

DDR Officials can be confusing. I hope I didn't muddy the water.

Dan