My grandmother in Iowa made coffee this way although she never specifically called it "Swedish Coffee". Big urn type coffee makers back in the day didn't have paper filters, they had at best an aluminum pan with small holes in it to allow the water to run through. Since you didn't have a paper filter, then how were you supposed to get a cup of joe without all the grinds in it as well? Easy, dump some eggs in there to bind up the grinds. The egg shells I would think cut down on the acidity and since they are made of calcium, they would absorb some of the acid, and you didn't have to bother with seperating the eggs with the shells, you could just crack them and toss in the shells afterwards. When the coffee was done brewing, all you had to do was scoop out the now boiled eggs and voila! That's how it was explained to me.