Call it a philanthropic time capsule.

If all goes as planned, 100 Minnesotans will contribute $25,000 to an unusual new charitable fund that will be sealed and invested for 50 years. In 2065, the vault will open and an estimated $23 million will become available for a blitz of community projects.

The fund is the brainchild of the Minneapolis Foundation, which concocted the idea when brainstorming ways to celebrate its 100th anniversary this year.

"We were asking, 'How do we honor our past, and how do we emulate our founders in the future?' " said Beth Halloran, a senior vice president at the foundation. "We thought this was a unique way to celebrate the centennial."

The Pay it Forward Forever Fund so far has attracted 43 donors — a mix of individuals, families and businesses, said Halloran. They not only pledge $25,000, they write letters and/or submit photos explaining why they made the donation. The documents will be saved in an "electronic time capsule" also to be opened in 2065.

One of the early investors was a man who wrote about his deep appreciation of Minneapolis parks and waterways.

"He wrote beautifully about how some of his best family memories took place in those spaces," said Halloran.

The fund will start with $2.5 million — assuming the 100 donors step forward. After 50 years, it will reach nearly $29 million, based on a 5 percent return and 2.5 percent inflation, the foundation calculates. Eighty percent of the fund's value, or $23 million, will be distributed to the community.

The remaining 20 percent, or about $6 million, will be reinvested for the next 50 years.

Halloran was not aware of any similar philanthropic venture. It is among a variety of ways the foundation is marking its centennial. On Friday, for example, it is sponsoring a Futurist Conference, featuring national leaders on the issue.

Although Pay it Forward is a fraction of the $740 million managed by the foundation, "it's a small but important part of our story," said Halloran.

Jean Hopfensperger 612 673-4511