The first printing of Magic: The Gathering, the Alpha set, is distinguishible from later Magic cards because of its unique shape. The corners of Alpha cards are noticeably more rounded than those printed in subsequent sets.
However, a small number of commons and uncommons from Fourth Edition were cut with corners rounded like Alpha cards. Because of their rarity, the "Alpha-cut" cards are difficult to obtain, and are sought after by collectors.
Card Type: Enchantment
Card Text: Untapped creatures you control get +0/+2 when not attacking.
Oracle Text: Untapped creatures you control get +0/+2.