Three batch 4 postcards from Nevada postmarked September 6th. All have unique pen markings in the upper right part of the postcard. This is why I started putting a volunteer number and postcard number on each postcard. There’s no telling when they are going to be placed or when they will come back.
160 EF08-01
161 Neostatic
162 Primrose
Return2.Me 
These are from me! In a roundabout way… I sent them with a friend who was going to Burning Man. I’m sad that they are blank… I thought that for sure the people in Black Rock City would have figured it out… 😦
This is rather mysterious. But not at all uncommon for this project. Thanks for trying something different.