Interesting letter from Mason's Challenge Blacking -- black and blue writing ink -- Philadelphia's primary purveyors of ink products in the mid-1800s. Because of rapid expansion, they were no longer sending sales reps into the field, rather they were soliciting business via correspondence. Beauitiful penmanship. Would be premier item save for the ragged bottom of the first page. Still, nice historic postal history item. Mailed to Henry & Douglass, Alexandria, VA.