The coin was deposited into a red kettle on Dec. 7 at a Kroger grocery store, The Detroit News reported.
"That just generated excitement in the room," said Maj. Kevin Van Zee, commanding corps officer of the Salvation Army in Warren. "We celebrate when we get a big bill, let alone a coin like that."
The rare coin weighs about one ounce and is worth about $1,200 if sold at gold value, Van Zee said.
"That would cover 10 people in a feeding program for an entire year," he said.
The anonymous donation was made just days after the death of famous former South African president and anti-apartheid activist Nelson Mandela.
"I don't know if somebody [donated the coin] in honor of Mandela, or if it's just a coincidence," said Van Zee. "The Krugerrand is the most popular coin [for collectors]."