Larry,
Welcome to SCF!
A word of caution-- be very careful -- stampless folded letters can be addictive!
The reference catalog for these items is the American Stampless Cover Catalog, last published in 1987. The U.S. Philatelic Classics Society purchased the rights to the catalog in 2005 and a revised edition is currently in work, with an anticipated publication date some time in 2012. (See
http://www.stamplesscovercatalog.com/index.html)The postmark on your stampless letter was used between 1833 and 1851 and has been recorded in both red and black ink. Additional stamped markings associated with this Angelica CDS (which should measure 30mm in diameter) were Paid, 5, 10, 10 in an oval, and Free. The value of the cover as listed in the ASCC Volume I is $8.00.
What I enjoy most about these old covers and letters is trying to learn about the writer and recipient. For example, here is a short bio on the addressee:
Quote:
The Biography of John Allen Collier
John Allen Collier, representative, was born in Litchfield, Conn., Nov. 13, 1787; son of Thomas and Elizabeth (Stockwell) Collier; and grandson of Richard Collier. He studied law at the celebrated law school at Litchfield, the first law school in the United States; was admitted to the bar in 1809; practised at Binghamton, and was the first district attorney of Broome county, June 11, 1818, to Feb. 25, 1822. He was a representative from New York in the 22nd congress, 1831-33, and comptroller of the state from Jan. 27, 1841, to Feb. 7, 1842. He was appointed one of the three commissioners to revise the statutes in 1847 and resigned Jan. 18, 1848. He was attorney for the receiver of the United States bank and was prominently named as the Whig candidate for governor of New York, refusing the second place on the ticket. He was presidential elector and president of the New York electoral college in 1849, voting for Taylor and Fillmore; and declined a foreign embassy offered by President Fillmore in 1850. He died in Binghamton, N.Y., March 24, 1873.
From: Twentieth Century Biographical Dictionary of Notable Americans, Johnson, Rossiter, editor
You also might recognize the signature of the sender, Gurdon Huntington, Jr., cashier of Allegany County Bank, on this note:

Thanks for sharing this,
Steve