I agree. The workmanship leaves quite a bit to be desired and the screws ruin the finished look and the clunky eagle fixture is oversized. The post-war period was awash in “Nazi” relics most of which never would have never made the grade during the Reich period. Here is a classic example of this kind of crap: http://www.bing.com/images/search?q=german+ss+nazi+paratrooper+knife&qpvt=German+SS+Nazi+Paratrooper+Knife&FORM=IGRE
I would say this is closer to the work of a reasonably competent amateur with a Nazi fetish.
I’ve seen another somewhere on the internet with 2 barrels that is similar, but also more believable - a bit cruder and smaller. Also to me (and you) the eagle looks unlike any other German eagle. If you search images of German buckles, none of the decoration looks anything like this one. I’m far from an expert, but you would think the documentation would trace it back to at least the 1940s. Some people love to fake this stuff, and it is easy to fake because who knows what it should look like, right?