Germany 1000 Mark / 1910 / With A Black Oveprint?

I don't know about your overprint, but I have two of these notes. One has red serials like yours, 7276668K. The other has green serials 4434682B. If somebody can answer your question, please would they give some thought as to why my notes have different colours.

Anyone know a good website for information on German banknotes?

As for the overprint, as far as I know it's nothing official. These banknotes rapidly became worthless during the hyperinflation, so I suspect it may have been used as part of a satirical poster or advertisement. The cut corner is cut at about the same angle as the writing, so I'm guessing the note was originally stuck onto the poster at an angle where both the overprinted text and the cut are horizontal. For what it says, there's too many missing letters for me to guess. The last word is "ist" (is), which doesn't really help much. Assuming the text is nicely centre-aligned, the first word is seven or eight letters long, and the second word four letters.