Office Equipment Identification

When documents have several features in common, it might be possible to state they were produced by the same typewriter, computer printer, photocopier, dry seal, rubber stamp, labeling machine or other mechanical device. However, if two documents which reportedly originate from a common source contain one significant difference, it is sufficient to prove the contrary is the case. 

Typewritten Documents

The following chart shows the typewritten date from a contested document (left) and specimens from a suspect machine (right). Damage to the digit "9" and dirt in the center of the "6" suggest both groups of documents were produced by the same typewriter.

Figure 1
Not only do the defective characters "9" and "6" indicate the questioned and known documents were produced by the same typewriter but they also provide conclusive evidence the contested document was fraudulently backdated. The damaged "9" and "6" are only visible on documents which were typed after July 2, 1996.  Both numbers are crisp and clear in the "July 2, 1996" date, proving the questioned document could not have been typed on June 12th, 1996.

Photocopied Documents

Dirt or foreign material on a photocopier's optical components (glass, mirrors, etc.) can produce "trash marks" (Figure 2) on copies produced by the same machine. These marks usually vary over time and can establish the approximate period when a particular copy was produced. In other cases, scratches to the copier's photosensitive drum will generate defects (Figure 3) of a more permanent nature.

Figure 2
(Click image for a larger view)

Figure 3
(Click image for a larger view)