Richards & Son appears to have long since trotted off into the sunset. I found a reference in the 1896 edition of The American Stationer to Richards & Son being "the oldest in this line of business in Atlanta" and it making preparations to move to a new location on South Pryor Street.
The back of the card (pictured below) features the full advertisement for Pride of the Mill. The copy states:
Here are some definitions of terms from the above passage:
MAY BLOSSOM PAPETERIE
AND "PRIDE OF THE MILL" FINE PAPERS.
To our Friends and Customers: We beg to call attention to a very handsome line of Box Papers at reasonable prices called the "May Blossom." We have it in a great variety of delicate tints, Ruled or Unruled; some Octavo but mostly Commercial Note size. The tints are as follows: Cream, White, Sunshine, Peach, Opal, Heliotrope, &c.
We can also supply the same papers by the Quire and Envelopes to match in the fine "Pride of the Mill" Papers.
- Papeterie -- An ornamental box for holding stationery. The word is French and dates to the 1840s.
- Octavo -- Octavo is a technical term, with a long and complicated history, used to describe the size and format of both books and paper. Check out Wikipedia's octavo page and the "Paper sizes" subsection of the Wikipedia's article on book size.
- Heliotrope -- According to Wikipedia, "heliotrope is a pink-purple tint that is a representation of the color of the heliotrope flower. The first recorded use of heliotrope as a color name in English was in 1882." (I'm a guy, so I didn't know this. Sorry.)
- &c. -- This is an old abbreviation for et cetera.
- Quire -- A quire is 1/20th of a ream of paper. A ream contains 500 sheets. So a quire contains 25 sheets.