Canon copier engine

[Eric Blossom]

> Steganographic signatures.  Similarly, signatures are being put into
> explosives  (although they are somewhat traceable already) by using 
> various mixtures of trace elements.

I believe that they also use small (microscopic) color coded chips of
plastic.  There is an OTA report on this topic with a name something
like "Taggants in Explosives".  I believe that the report is about 10
years old.