An Impact Engraver is just as the name implies. It marks by impacting the surface with a diamond tipped tool at a very high rate of impact per second. The precision and accuracy can allow for 26 digits of a bar code in a 1 square mm space (0.0393" square)
Impact engravers are also referred to as Impact Photo Engravers. With their precision and high DPI, photographs can be engraved on a wide variety of metals.
Here are a few examples.
This measures only 1 inch tall bt 1-1/2 inch wide yet has the complete Gettysburg Address imprinted on it.
New Zippo Lighter
Very old Zippo Lighter
Photo of the ring from
Lord Of The Rings