Undated cover, now in digital captivity at the American Book Trade Index.
Isaac P. Cook
Bookseller and Stationer
76 Baltimore St.
All inside a calligraphic swirly. Addressed to WW Harding, Publisher, Philadelphia.
A Baltimore City Directory places Cook at this address (actually W. Baltimore St.) in 1845.
Maryland Historical Society has further info:
COOK FAMILY PAPERS, MS. 2328
Land transactions of Isaac P. Cook (1808-84), Baltimore bookseller and stationer, and his wife, Laura (d. 1876), and daughter, Isabel (fl. 1877-87); correspondence, 1877-80, about property assessment; deeds for Baltimore City and County land, 1808-87.
47 items, 1808-87
Cover posted to ebay here. Sold for under $3. Very little. At that price, I should have grabbed it, but I thought it would go higher. I can always console myself it is out of my collecting area... but I don't feel any better about it...
WW Harding was bankrupt by 1878, according to this article from the NY Times.