manuscript postmark with blue "Paid" handstamp and manuscript "12½" rate on 1842 folded letter to Koshkonong, Wisconsin Territory, vertical filefolds, very fine, illustrated in Piszkiewicz (page 3)This cover is the only recorded Chicago manuscript postmark from 1842 and one of just two known from the 1840s. It was mailed between the latest known use of the A-2 postmark device but before A-3 entered use, suggesting the Chicago post office was without a handstamp for a short time. However, the fact that the A-2 device reappears in 1843 and 1844 seems to contradict this theory. There is also the possibility that this letter arrived at the post office shortly before closing, after the postmark had been locked away for the night. While we may never know the definitive answer, this cover remains a unique and important piece of early Chicago postal history.