Classic & Vintage - Early 70's (?) "Hercules" German city bike?

I came across an unfamiliar bike today, a German-made "Hercules" commuter bicycle in a relatively large (25"ish seatpost) men's frame. I've had next to zero luck finding information about it online, just a casual reference to the Hercules brand being fairly common in Germany and that it's probably of decent but not spectacular quality. I did find a very similar looking headtube in this thread (the blue and white one with unusual lugs).

http://www.bikeforums.net/showthread.php/690540-Head-Badges-calling-all-Head-Badges!?highlight=hercules

With German bikes being uncommon here, would one of these be a pain in the tail to maintain? Anyone out there have experience or information on the German Hercules bikes? Did they make their own frames?

I'm pretty sure the German Hercules made their own frames, and probably some of the other components. There shouldn't be any problems with maintaining one here. If it comes with Woods valves, you can change them to Schraeder no problem. The tires may be a little hard to find (i.e. Walmart might not have them) but again, probably not a problem. If you're looking for a large commuter bike, it might be just the thing for you.

If you get it, post photos, please!

I've worked on a couple at the co-op and they seem to be great bikes and the one I worked on had 590 rims so no worries there. Everything else looked normal.