A photo showing $100 bills being counted out.Kham/ReutersA secretary bought three shares of her company's stock for $60 each in 1935.Grace Groner reinvested her dividends for 75 years, and her stake ballooned to $7.2 million.Her employer, Abbott, shared Groner's story in a recent website post.A secretary paid $180 in 1935 for three shares of her employer's stock.