OK, I wanted to give you an update regarding this matter. I contacted Norman Brosterman. This was his answer: "I have folds dated 1874 from St. Louis. Made by American kindergarten teachers."
A member on the list offered helping me contact Joan Sallas. Hopefully he has pictures of Senff's models in display in German museums and have a good idea of how old they are. I'll let you know once I contact him. Karen, did you have any luck getting a picture of Linnaeus's fold of the seed packet from 1778? Guys, any idea of how we can contact Koshiro Hatori or the Moriwaki family regarding the folds from the first decade of the XIX century that the family owns? There has to be a way. Another member on the list mentioned me the Turin papyrus map as the oldest preserved fold. There's information here about the map: https://en.wikipedia.org/wiki/Turin_Papyrus_Map According to the information there, it might have never been folded: the apparent creases might be a consequence of the deterioration of the paper. Besides that I personally would say the map isn't well-preserved, and even if it was, in my own opinion the traditional method for folding a map isn't origami, but that's just what I think : ) This centuries old folds might offer us tips about how to best preserve our best folds. Just a thought ; ) Gerardo gerardo(a)neorigami.com PS: Thank you for the tips regarding the drinking cup; It has been really useful. I'm doing some tests. If you're interested, I also started a very interesting thread about the models capacity in The Origami Forum: http://snkhan.co.uk/forum/viewtopic.php?f=12&t=13674