The blank pictured below sold in Europe this weekend. Perhaps it sold to a Forum member. I have some information on this round that may be interesting to the new owner.
I am pretty confident this is not a WWI blank. Rather, I think it is probably by RWS in 1924. Over 40 years ago, a German friend, no longer a collector, had access to an RWS laboratory storage area and found this style of blank and information indicating they were part of an experiment from 1924 with red paper bullet blanks. This is the same lab that had the partial box of RWS made wood bullet blanks that were mercury filled. He came away with two specimens, one unheadstamped with a plain red paper bullet which looks like the one illustrated below, and another with a lacquered red paper bullet and a Spandau headstamp. He told me that both types were on mixed WWI cases so the headstamps had no meaning. I still have his note in my files and the rather poor photo he sent. He traded the two blanks to a collector here in the US and that collection was later bought by another collector. I have examined the rounds when they were in both collections. One had the tip slightly smashed which could result in the same type of tip damage seen in the photo below. The RWS Lab was known to allow some well connected people to come in and leave with a sample or two. That is why the box with the mercury filled bullets, which is now in a museum, has only two rounds. It was well over half full when a very well connected collector got his over 60 years ago. I understand that the 9mm illustrated was from a collection of an elderly German collector who has been collecting for many years and was likely well connected. He likely could have gotten this cartridge, directly or indirectly, from the RWS lab.