51 and.... I discovered a "combo" in my deck. It means I need to get all my cards out of my library first and then cast seasons past.
Reason: Seasons past returns any number of cards with different mana costs from my graveyard back into my hand but instead of it going into my graveyard, it goes at the bottom of my library.
Which means that I now have a full hand and I can do the same thing next turn. Its dangerous and hard to pull off (After all, a commander deck is 99 cards) but it does mean that for the low low price of 6 mana I get more than a full hand.
Also, I have things that work well with suddenly getting that many cards in hand from my graveyard. For example Descrecated tomb (which gives tokens if I get stuff out of my graveyard) but also saproling cluster (which I can use to turn the expensive stuff in my hand into 1/1 tokens) and Crawling sensation (Which also creates a 1/1 token but does so whenever a land goes into my graveyard. For example because I discard it for saproling cluster or simply because my hand is too full at the end of my turn)
I also have baneful omen, which is guaranteed to reveal Seasons past in this scenario meaning that I do 6 damage every turn to EVERY opponent.
I'm not saying its a good combo (if you can call it that) but if I manage to pull it off it would most likely be hilarious. Too bad even my own commander would kill me if I'm not careful in that situation
Or... a howling mine, a temple bell or a "target opponent draws one card", etc,etc