Old School 40 (OS40) is an invitational tournament that uses the Eternal Central Old School 93/94 rules with the following modifications:
1) 40 card minimum deck
2) All restricted cards are banned
3) Strip Mine is banned
4) No Sideboards
We are also fast and loose on the "original printings" requirement. Instead, any card that was printed in any of the legal sets is allowed, in any printing. Ideally, players would use cards with the original images, but hey, we can't all be perfect.
Matches are best-of-three, round robin.
Prizes are traditionally a number of basic lands equal to the number of players, drafted in order by winning record. All prizes are signed by all players and commemorated with the invitational event name and year.