Brass lock developed by Eagle Lock Company of Terryville CT. The front of the shackle was stamped "U.S. MAIL" by the manufacturer. “EAGLE LOCK CO. TERRYVILLE, CONN." was stamped above the keyhole in an arc over “PAT’D” over “1863 & 1870.”
This lock is an updated version of the older Star Route registered mail lock also manufactured by the Eagle Lock Company based on patent number 104,572. There are differences between this lock and the earlier versions. On this lock the front and back are heavy brass plates, and the earlier locks were thinner metal that formed two halves. The shackle on this version is heavier. Like some of the Star Route locks, this one has the offset double-bit keyhole. This allowed some security in that keys from the older design would not work this lock.
This is a heavy, well made lock. Because it provided more security than the more common locks, it was probably used for securing registered mail or on longer or more important routes.
U.S. Patent and Trademark Office
“Early Locks and Lockmakers of America,” by Thomas F. Hennessy, Nickerson & Collins Publishing Co., Second Edition, 1976.
“Illustrated Catalog and Price List of Padlocks Manufactured by Eagle Lock Company,” 1905.