From publisher blurb:
1E Heroic Abilities allows characters of any class to increase prime requisite ability scores. This 6 page supplement for OSRIC™ and other 1E games adapts the concept of ability score increases and applies them in a manner consistent with the spirit of First Edition rules.
Learn how your 1E character can increase certain ability scores by class. Discover the benefits of exceptional scores other than "percentile Strength" and use Heroic Effort to increase abilities at critical times!
But don't worry; these rules support the spirit of the old school! Chance plays a part and the supplement avoids easily stackable bonuses that (from a 1E perspective) could easily spin out of control.