Hard to find history on many German companies from that era, I guess due to the negative associations with their war efforts.
Wikipedia suggests that August Rabeneick did not start making bicycles until the 50's, so I don't think it's worth what the eBay man is asking.
Looks to me like a low-end 60's bike that was rattle-canned to hide rust. I could be wrong, though, but I don't think so.