Finding multiple uniques

[whathuh]

Reading online, I found that a unique item can never be dropped more than once in a the same game. Does that mean you can't find 2 unique rings in the same game or just cant get the same TYPE of unique ring. To put it into easier terms for me to understand, if andariel drops a nagelring, will all further unique rings be manald heals and sojs (for the case of levels under the qlvl of dwarf and raven), or will they only be rare rings. And if in that same game another nagel ring were supposed to drop, would it revert to a rare item or would manald heal and soj have a better chance of dropping? If the latter is true, then 3 unique rings found from monsters under the qlvls of dwarf and raven would all be a nagel, manald, and soj.