SALINA, Kan. (AP) -- Saline County officials got a nice surprise recently when a rusty old tractor they put up for auction online brought in more than five times what they paid for it 40 years ago.

The 1970 Industrial International sold this past week for $56,100 on the Purple Wave auction website, The Salina Journal reported (http://bit.ly/MfwIEl ).

The tractor, which Saline County bought for $9,607 in 1970, was among several items that the county auctioned off to make money for new equipment. Other items included mowers, trucks, road graders, air compressors and bridge planks.

Bidding on the tractor took Saline County officials by surprise. Apart from being 40 years old, the tractor has a dead battery, rust spots, cracked front tires and areas caked with hydraulic fluid sludge. But it also has a 6-cylinder diesel engine and a loader with a 7-foot bucket.

The phones at the county's road and bridge department were "going crazy" on the morning of the auction, said Darren Fishel, county road superintendent.

He said people interested in the tractor were looking for more information.

"We're just amazed," Fishel said.

York Hekel, Purple Wave customer service director, said in an email that the winning bidder didn't want to be identified.

"The item has almost immediate interest and bidders from around the country," he said.

The first $10 bid was posted on June 5 and after that the tractor's price took off with interest from 14 separate bidders from Kansas, Iowa, North Dakota, Colorado, Texas, Nebraska and Michigan.

A 2012 model tractor from Case-IH would cost between $43,000 and $45,000, said Bruce Spidle, general manager of Straub International in Salina. International Harvester merged with Case in 1985. He said the county's old tractor is likely sought by a collector.

"It's for restoring it as a collectible. In a lot of ways, it's an investment," Spidle said.