I've only recently begun to collect stampless covers (this is my second acquisition) and I'm finding that they are really quite fascinating when you're able to get a glimpse into the life of either the sender or the recipient.
There was no letter associated with this cover but I imagine it was most likely an order for the Dr.'s "celebrated cough remedy" (his opium-based catarrh remedy wasn't developed until 1876).
Absent a dated letter, I think I've been able to narrow the window of mailing to between 1849 and 1851 on the basis of domestic letter rates and 1849 being the the patent date for the first envelope-making machine in the U.S.
