What is the purpose of the emancipatation letter among the old couple's belongings in Invisible Man

The old couple is being evicted yet the emancipation letter is a reminder that they were once slaves,

"Be it known to all men that my negro, Primus

Provo, has been freed by me this sixth day of August, 1859. Signed: John

Samuels Macon . . ."

They were free to live the American dream; this is what their dream turned out like.