By Jeremy Ross

(CBS) — A rare coin is helping change the future for an Indiana church.

The mystery person does not want the recognition for her good deed, but she talks with CBS2’s Jeremy Ross.

Piles of dirt and construction equipment will eventually be replaced by worship and song.

The $3.5 million plans for Gracepoint Church include an auditorium for more than 500, a kid’s center and a lobby.

Pastor Ben Lamb says his congregation was outgrowing the space at a nearby elementary school, and they needed $300,000 to secure a building loan.

And then a kind of angel showed up.

A woman provided the money with a single coin: an 1866 Double Eagle $20 dollar gold coin, a one that was never in circulation.

The donor – she asked CBS 2 not to identify her by name — says her late husband an avid coin collector, bought it decades ago for $125,000. These days, at auction it could go for $300,000 or more.

The woman downplays her gift.

“I have a roof over my head, I’ve got food in my mouth. I can get by just fine. I’m not looking for wealth. I’m just looking to be comfortable,” she says.

The coin goes up for auction April 27 in Schaumburg.