I hate to say this, but I'm sure you suspect it;

But it looks like someone took a set of stamps to it, particularly at the beginning around the "OB2" where it was restamped over and over and over again, it looks like its been redone 5 or 6 times, its highly suspect. Also the depth on those stamps are really deep and heavy, compared to the original average stamps with 30+ years of age on them. Unfortunately, that doesn't look like a factory restamp to me.