Found this cute little buckle at the 1820 house I've been hunting in between rain showers. Just looking for what kind of buckle this is and what time period it may have been used in.
Your dug-at-an-1820s-housesite iron buckle's size is too small to be a pants-belt buckle... so it is most likely to be a generic buckle for a leather strap, probably a horse-harness buckle.
About its time-period: That shape of iron buckle has been in use for centuries. Although yours was dug at an 1820s site, there's no way to know whether it was lost in 1823, 1883, or 1923 (etc.).