Here is the official Wikipedia answer on "chops":
A seal, in an East Asian context, is a general name for printing stamps and impressions therefore are used in lieu of signatures in personal documents, office paperwork, contracts, art, or any item requiring acknowledgment or authorship. China, Japan, Taiwan, Korea, andVietnam currently use a mixture of seals and hand signatures, and increasingly, electronic signatures.
Chinese seals are typically made of stone, sometimes of metals, wood, bamboo, plastic, or ivory, and are typically used with red ink. The colloquial name chop, when referring to these kinds of seals, was adapted from the Hindi word chapa and from the Malay word cap meaning stamp or rubber stamps.
I think that is really interesting that the seals are printed with red, similarly to red wax seals used in the West. So many things are vastly different in the East and the West, yet on this they are the same. I remember watching "Where in the World is Matt Lauer?" on the Today Show in high school when he visited the Vatican. He said that one of the explanations for the origin of "red tape" (i.e. "She had to get through a lot of red tape to get her passport") was because of all of the red wax seals that would be affixed to red ribbon at the bottom of official documents. So, apparently it doesn't matter where you are in the world, East or West, everyone has "red tape" to work through!