The story of a never-married secretary who left $7-million in her will to her alma mater is still making the rounds—in fact, the ABC news anchor Diane Sawyer noted the gift in a recent piece called “Secret Donor.”

Grace Groner had quietly amassed a fortune with a single investment: Back in 1935, she bought three shares of stock, each worth $60, in Abbott Laboratories where she worked; it grew to $7-million.

But no one knew that Ms. Groner, who died at 100 years of age, was a multimillionaire until her extraordinary gift to Lake Forest College was announced. She lived frugally in a tiny cottage that was worth about $150,000.

Still, there were clues that could have tipped off a savvy fund raiser, even though development officers and the president of Lake Forest had no idea the gift was in the works, writes blogger and direct-marketing expert Roger Craver in The Agitator.

For one thing, Ms. Groner enjoyed attending events at her alma mater, as Ms. Sawyer’s report noted. For another, Mr. Craver writes, she made frequent small gifts to other local causes, as he discovered by using a research service that tracks donors’ past gifts. Small, frequent gifts, as fund-raising experts like to remind people, are a key characteristic among donors who eventually make charitable bequests.

Those characteristics, and the fact that she was childless, are strong indicators that Ms. Groner was an excellent prospect for an estate gift.

Few could have predicted, however, that she would leave everything, including her home, to the college. The money is being used to establish a foundation to help pay for the college’s students to study abroad. And Ms. Groner’s home, now called Grace’s College, will house scholarship students.