I have had this Primus 1020 for over a year, and just figured out that the spirits cup fits in the slot on the generator nut... I did not figure it out until I saw pictures over here.
Primus usually had some very well designed lamps and stoves, but the fitting of the spirit cup for the 1020 (and all the others) is terrible.
Actually the fitting is good, no need for extra hardware, but it was completely counter intuitive to what I was used to...Petromax are screwed to the center stud, Coleman has a cup that goes around the generator with a small clip to the air tube that prevents the cup from smashing the mantle if one puts it upside down. I had it secured with a small piece of safety wire to the air tube, but it was not very secure, rattled around once in a while, and had broken the mantles several times while fiddling with the lantern...now it is where it was supposed to be...
As far as I know, Primus lamps are the only ones where you can lose the spirit cup. All the others have it fixed in one way or another. It gives a problem today as a lot of Primus lamps are missing their spirit cup and spares are non existant.
Well, with Tilleys you can lose the priming torch which is equally annoying (but less likely to destroy the mantle!)
I thought one would be enough, then two, then... Thank goodness for Stu's preheater cups that don't wander off!