It wasn't just fax machines. Throughout the Eastern bloc, typewriters were strictly controlled and registered. There's a great scene in The Lives of Others [1], a German movie about a Stasi agent and a dissident writer, in which the Stasi (East German secret police) have recovered a typed manuscript that was smuggled to the West, and are interviewing a forensic expert to determine the make/model of typewriter used, in an attempt to cross reference against anyone who owns that typewriter.

We still do similar things now, though for ostensibly different reasons. Inkjet and laser printers have long had various signatures they add to every printed page, barely noticeable to the naked eye, that can lead back to the specific printer used. The stated motivation is to prevent counterfeitting. Similarly, there is a pattern of "O" symbols called the EURion constellation that, if present in an image file, most commercial image editing software will refuse to print [2].

It's not surprising that politicians are trying these sorts of strategies with 3D printing, because they've already tried and used them often in the past.

[1]: https://en.wikipedia.org/wiki/The_Lives_of_Others

[2]: https://en.wikipedia.org/wiki/EURion_constellation#Counterfe...