Something to do with the CSS Alabama in Fort Beaufort, Eastern Cape, South Africa? Apparently so, according to this write up:
In summary (because Google is not yet skilled at OCRing the content of photographic images), there's a shell in this museum reportedly fired from the CSS Alabama at the coastal hamlet of Hamburg (which is near the villages of Berlin and Potsdam). All of these are in the Eastern Cape near East London.
Here's the object in question, with an adult male human hand to give some scale:
Colour me slightly sceptical. The Alabama, according to some superficial Internet research, had as it's major armament feature a 100 pounder 7 inch rifled Blakeley swivel gun. While I only discovered this after returning to Grahamstown, the above pictures show the shell could be easily about 7 inch caliber. I haven't the faintest idea of the weight of it, but it could easily be about 100 lbs or 45kg. Some less superficial Internet research failed to turn up any images of the projectiles fired by this type of gun.
My burning question, though, is: Why is the above shell complete and not being displayed in the form of a pile of shrapnel? I also have a mental picture of civil war artillery being more of the "cannonball" variety, so this thing looks a bit too modern. But then we're talking state of the then art "rifled gun", so it'd need to be firing something a bit more exotic than an odd looking cannon ball.
A less burning question is who would waste their time by firing anything at all at Hamburg, despite it being full of German missionaries? Maybe the Alabama was training and didn't notice there was anything there - which could also explain why the shell didn't explode.
Can anyone confirm or deny the claims made in the photographed article? This museum contains Congreve rockets of more sophisticated configuration than the traditional scaled up bottle rocket with side mounted stick, so anything is possible.