German: Same Stamps Different Perfs

Well I bought a bunch of the German hyperinflation stamps and noticed that some have the perforated "holes" and I see that some have the "zigzag" like perforation.

Which is more common?
Why two different perforations?
And lastly, what is the numbers on the selvage of the stamp, looks like an overprint number?
I hope I have posted to the correct folder (World Back of Book)
Thank you!
Sue

The zig-zag is roulette perforation. The Germans made extensive use of it during the inflation period. On this particular issue, both types of perforations are common mint, but the rouletted is rarer used.

The numbers in the margin allow for quick counting of the value when separating blocks of stamps from the sheet. Note that those you show increment by 2, the value in millions of each stamp.

Neat blocks, Sue.

The selvage on German stamps is often more interesting than most...typical German efficiency? You be the judge.