A chop is a signature or identifying mark made by a furniture or cabinet maker to identify his work. In the 18th and 19th centuries, cabinet makers (sic) furniture

Furniture

Furniture is the mass noun for the movable objects intended to support various human activities such as seating and sleeping in beds, to hold objects at a convenient height for work using horizontal surfaces above the ground, or to store things...

 makers were allowed to use their own individual chop to identify their work only when they had qualified as a Master Cabinetmaker. This practice originated from the Chinese tradition of seal

Seal (Chinese)

A seal, in an East Asian context, is a general name for printing stamps and impressions thereof that are used in lieu of signatures in personal documents, office paperwork, contracts, art, or any item requiring acknowledgment or authorship...

s called "chops" and was introduced to Europe in the middle ages.