Cannot Find This German Stamp In Michel

I am not collecting older German stamps (before 1945) and know nothing about them. I just found one stamp that I cannot find in Michel. Am I missing something? If this is fake - why to fake non-existent stamps?

This looks like it comes from the Hindenburg memorial set of 1934 4 Sept which is 6 Hindenburg definitives with black borders. But it isn't. Check out the uneven borders, they've been hand-drawn, maybe as a personal memorial? Here's the set as issued. Mi 548-553

Looks as if someone decided to expand the basic set by adding a 20 stamp, whether to amuse or con. In a slightly different vein, I sometimes see Edwardian cigarette cards (which often had black surrounds, especially for photographic series) "improved" by inking in the parts of the edges where the original surface has been damaged. My ebay lot below is an example of something that looked good at first blush, then quickly became a disappointment!

http://www.ebay.co.uk/itm/371774334....m1555.l2649

Does it look like the cancellation is over the blackened margin? I'm looking specifically at the lower left corner. If so, it would suggest that the sender created his own Hindenburg mourning stamp after having run out of the official ones and posted the letter.