This one perplexes me!
2d.Point for example about registration mark's hidden feature (6,3). Answer is Easter Egg but cannot see anything to suggest this.
Easter egg noun 1. an artificial chocolate egg or decorated hard-boiled egg given at Easter. 2. an unexpected or undocumented feature in a piece of computer software or on a DVD, included as a joke or a bonus.
Easter egg
noun
1.
an artificial chocolate egg or decorated hard-boiled egg given at Easter.
2.
an unexpected or undocumented feature in a piece of computer software or on a DVD, included as a joke or a bonus.