The envelope was just one of many among the invoices and other business correspondence Kristi Amend handled at the Richfield Police Department one day last month.

But this one was different. Inside was a Western Union money order for $100 simply made out to "Police Richfield."

Last week the City Council formally accepted the donation, directing it to a fund that goes to pay for crime prevention and things like bullet-proof vests for police.

Anonymous financial contributions to cities aren't very common. In Bloomington, people sometimes send in small cash donations in the range of $5 to help pay for the fireworks display at the city's Summer Fete celebration. But officials in Minnetonka, Hopkins and St. Louis Park all said they don't remember recently receiving such gifts. In fact, donors often relish the recognition and public thanks they get at City Council meetings, where their gifts are received and acknowledged.

Amend, an administrative assistant in the Police Department, said this isn't the first anonymous donation Richfield police have received. The money order didn't arouse her investigative instincts, and she didn't check the envelope for a postmark or other clue to the donor's identity.

"It was just one of those things where I thought, 'That's really weird; there's no name, somebody wanted to make a donation and that's really nice,'" she said. "It was amid the invoices. I just wanted to get it in the right bank."

Amend said that in the past, people sometimes have sent anonymous donations for specific programs. This one stood out because it wasn't earmarked for anything.

Could it have been from someone guiltily remembering and trying to make up for a childhood transgression? Did the odd use of "Police Richfield" indicate it was from someone whose first language was something other than English? Was it mailed from Pago Pago or Leningrad?

Amend thought it more likely that it was a thank you from someone who appreciated the work the police had done on a case that affected them. Or perhaps it was sent by a parent who appreciates the anti-gang work the department has been doing among youth.

"There's limited funding for those programs," she said. "Maybe they want the program to continue, but don't want to draw attention to themselves."

Mary Jane Smetanka • 612-673-7380 Twitter: @smetan