Diamond point engraving was a technique developed by the Dutch
back in the 1600's, before mechanized engraving.
It is performed by scratching the glass with a diamond, each scratch creates a
white line, allowing the creation of an image.
It is very difficult on the hands to scribe the glass, due to the great pressure
The other technique is traditional glass engraving, with water
cooled stones which spin on a lathe like tool.
The crystal vessel being engraved is held in the hands, and moved against the
spinning stone, which cuts into the glass.