Your find is indeed part of a two-piece Tongue & Wreath style belt buckle. These buckles are made of die stamped rolled brass, and date from the 1850's. This particular design featuring an upright eagle, clutching arrows and an olive branch on a lined field, surrounded by a rope border, is commonly referred to as the "Stamped Brass Rope Border Eagle Buckle" by collectors. There are actually three outer wreaths, that are the correct fit and match for this particular buckle center tongue. The most commonly encountered wreath, is entirely plain and smooth. The next wreath features a lined or reeded edge design (much like the edge of a coin). The rarest outer wreath, and one that provides a clue to origin on these particular buckles, is one marked Bondy Brothers & Co., on the belt loop.
From historical accounts, we have the following information on Bondy Brothers & Co:
Joseph & Adolph Bondy, Bondy Brothers & Co., New York City
Addresses: 126 William (1852), 162-163 William (1853-54), 73 William (1856-58)
The brothers originally began their business dealing in liquor in 1849, then by 1851 they were manufacturing belts. By 1852, they expanded into military goods, as well as manufacturers of belts, gloves, and shirts into the early 1860's.
CC Hunter