Bear in mind that typewrites have been traced by the minute, unique characteristics of the metal face of character producers, whether lever-type or ball. The FBI has been doing this quite a while. Micro-forensics of the unique printing mechanism of each machine is likely possible. Identification in this manner would have nothing to do with toner cartridges or machine numbers, although it would probably take a sophisticated laboratory to make the match. As with most intelligence involving technology, it is not the obvious that reveals but conceals the less than obvious, at several depths of deception. Software registration numbers don't mean much compared to what is snarfed when you log on to register a product -- not to mention those sneaky handshakes of PKs and TTPs and SSHs and Extra-Secure Certificates. Take a gander at a Wash Post Op-Ed from a few days ago that explained what has been explained years ago on this sacred list about technological and intelligence deception, in particular the role of media yokeling the public: http://cryptome.org/intel-pr.htm To be sure the Op-Ed, written by someone at MIT's Security Studies Center (wah!), may be an example of what it speaks, but not this message from god: there will be no casualities, James, dogdamn it, no pain and suffering, just lip flapping about the horror deserved.