Stolen or fake usmc marked kac rear sights, amazon seller.............

These things seem to pop up on eBay for around $45-50, and are the real deal from what I've seen. No idea if they are stolen or not, but sellers often have a buttload of 'em.
 
And for the companies buying them back in bulk for refurbs as these things are getting sold? There is tons of surplus if one knows where to look. I know a guy in California who buys stuff via DRMO and cleans and sells stuff just like this. The one on Amazon isn't his, but I have bought a BUIS from him in the past.