Your buckle looks the same as all of them that I have seen or handled over a fairly long period.  That only means that if it’s a fake it is a good one and identical to an original.  Since it looks like mine, it is an original.  I don’t recall a lot of controversy about these cast brass buckles, but there is or has been a lot of speculation over a stamped brass H-design buckle that was patented in 1881 by Mills and manufactured by Orndorfff, his brother-in-law.  They made a popular model of the same type for the sportsmen, the most popular being a dog’s head design iinstead of the “US”.