welcome from the Fort Sumter and the Fredericksburg forums.
I'm no expert on them at all (far from it), but from others I have seen posted on here and discussed this one looks like a reproduction. @UCVRelics can say for sure.
Lucky you. Must of had the luck of the Irish with you this weekend. Lost count of folks on this website spending big $ on items only to find out it's repro ****!
@b804 Welcome to the forums! If you are interested in buckle collecting, there are some great books we can share. If you ever come across any more, what you want to look at are a few things. US buckles come in three sizes and have three types of hooks you can encounter. Wire hooks, puppy paw studs or arrow hooks. The arrow hooks come in just a few slight variations but the key things to look for are arrows that have rounded edges that are beveled. The singular hook, with the exception of the Boyd patterns are rounded. The lead solder fill in the back should be somewhat sunken in sometimes, not totally flat across the plate and definitely not overfilled past the rim.