When I did at last turn my eyes in Wemmick’s direction, I found that he had unposted his pen, and was intent upon the table before him.
– Charles Dickens
Great Expectations, Chapter 51. The metaphor of Wemmick “unposting” his pen is used to describe him having finished using his pen. The pen is likened to a letter ready for sending but not yet mailed. A number of times in the novel post office and mailing images are used to describe the behavior of the lawyer’s clerk. They serve to highlight his focused attention and dedication to his work.