here's some info i found:
The south imported as many items into their war effort, from cannon to cartridges, rifles to powder, bullets to belts. Among the plates imported from Britain were their classic "snake" belt buckle, referred to as such because of the "S"-shaped animal used as the loop connectors of the two belt loops. Some styles were indeed true "snakes," while others were snakes with duck-heads (like this one), and variants of multiple styles and types. The British military used them, as well as private British makers made them for retail. Then, within the South, there were local makers of these "snake" buckles to boot. A lot of "snakes" around! It is also very true that this British "snake" buckle style continued to be made and utilized throughout her majesty's empire/colonies for many decades after the war. Sadly, many "snake" buckles are being passed for "Civil War," though many were made long afterward. And with so many variations known to exist from the War, it is hard to determine whether a plate is "period" or not by the size or style alone. BUT, with the construction of the brazing of the "loops" that the "snake" hooks into, we KNOW this is STRICTLY CIVIL WAR PERIOD!!! Dug specimens are nice, since they tell you it was found within a camp or battle. But non-dug ones abound from many places. This one measures 45mm by 72mm--which is the size of the snake buckle in Mullinax's CS Belt Buckle book, Plate 206 (though a different style). What is nice is that regardless, they are an affordable option for collector's to exemplify one of the South's well-used plates.
http://www.championhillrelics.com/bucklesplates.htm