Here is a short article about which copy program can copy it’s self. I’ve said it before I always judge copy programs this way BITD. I figure if the program can not even copy it’s self, then it can’t be that good.
C64 Copy Protection
Documenting the History of the Commodore 64 protection scene
Di Sector, notably, gave you a “master disk” that could write three protected copies of the copy program. These copies would not copy themselves, nor the master disk.