Every typewriter has a unique signature as has every other polygraphic machine (fax, printer, copier). This was a case always, after Media burglary (in the '70!

Every typewriter has a unique signature as has every other polygraphic machine (fax, printer, copier). This was a case always, after Media burglary (in the '70!) FBI was collecting Xerox copier printouts to identify where the burglars reproduced the stolen files.