The Legal Sets are: Alpha, Beta, Unlimited, Revised, Arabian Nights, Antiquities, Legends, The Dark, Fallen Empires, Collector's Edition, and International Collector's Edition. All reprints of those cards with the original art and original border are also allowed.
Each deck must contain 60 cards and be singletons (i.e. not more than one of any card) with the exception of basic lands. There are no sideboards in Old School Singleton.
The following cards are banned in Old School Singleton:
Ring of Ma'rûf is legal, but you may only use it to get a card that is legal under the above rules and that you do not already have a copy of in your deck.
We have special errata for Falling Star. Falling Star's errata is as follows: "Choose any number of non-token creatures on the battlefield, then arrange them in the playing area in any way except that none of them may overlap. Flip Falling Star onto the playing area from a height of at least one foot. Falling Star deals 3 damage to each chosen creature it lands on. Tap all creatures dealt damage by Falling Star. If Falling Star doesn't turn completely over at least once during the flip, it has no effect."
Chaos Orb has the same errata as set forth by Eternal Central rules.