Ohio State first used Buckeyes on helmets in 1967. Even though quite often 1968 is mentioned as first year. Fact is they used them on the 1967 scarlet helmets.
I was checking out todays Uni Watch column and saw this article about Rutgers using stars for interceptions in 1961. Miami Ohio also claims it used award stickers 1964 or so.
I recently found some info on the Buckeye leaf as a symbol for Ohio State athletic equipment or clothing. I will find that and post in time.