At first blush, two $20 bills placed side by side certainly appear authentic enough that neither would make a cashier do a double take while working the window of a busy drive-through at a fast-food restaurant.

At first blush, two $20 bills placed side by side certainly appear authentic enough that neither would make a cashier do a double take while working the window of a busy drive-through at a fast-food restaurant.

But held up to a light, only one has the ghost of Andrew Jackson on the right-hand side.

The image is called a "watermark," proof that one of these two $20s is legit and the other is not.

"Hands down, that's the best way to tell," Medford police Sgt. Brent Mak says. "There's no security thread, no watermark, because the counterfeiters can't replicate that."

But it certainly hasn't kept them from trying — and succeeding — to pass them off as real.

The Rogue Valley is getting papered with counterfeit bills this year, and trying to keep all that funny money out of circulation is no laughing matter.

Medford alone is averaging more than a case a day and is on pace to nearly double last year's tally of 302 counterfeiting cases, which was up almost two-thirds from 2011.

"It's way over the top," Medford police Chief Tim George says. "It's becoming a booming business, and we're trying to stem the tide."

Throughout the country, $80.7 million in counterfeit currency was passed and detected in the federal fiscal year that ended Sept. 30, according to the U.S. Secret Service, which investigates counterfeiting cases.

In Oregon, 14,586 fake notes valued at $516,374 were passed. More than 1,000 notes, valued at more than $31,500, were passed and seized in September alone, according to the Secret Service.

The numbers and values of the passed bills fluctuate month to month, but Oregon as a whole has not seen a significant change in cases recently, says Jon Dalton, resident agent-in-charge at the service's Portland office.

Medford's location, however, makes it prime for counterfeiters looking to pass bills.

"You're right there on the California border and right on that I-5 corridor," Dalton says.

The bills get passed at fast-food restaurants and larger retail businesses to cashiers who are either too busy to check the bills for authenticity or are simply fooled by their appearance, police say.

Counterfeiters are known to pull into town and hit a half-dozen or more fast-food restaurants in an afternoon of laundering phony bills.

"They'd go to a restaurant, buy $7 worth of food, pay with a $100 and get $93 back in real cash," Mak says.

The bills often get discovered when the recipients attempt to deposit the fake money amid their normal receipts at local banks.

"They're getting harder to detect, but we train our team members to look for signs of the bills," says Fawn Jones, branch manager of the Wells Fargo Bank in White City.

Jones' branch saw a spike in counterfeit $20s and $50s this past summer. Bank representatives cull them from deposits and notify police.

"It was so bad that businesses quit taking $50 denominations," Jones says.

The last one to take possession of the bad bill ends up the victim in the case.

"It's the store owner who takes the hit," Jones says.

Police at least slowed the flow of counterfeit cash, albeit briefly, on Oct. 12 after Medford motel workers discovered a bag loaded with $3,000 in counterfeit bills in denominations from $5 up to $100 in a recently vacated room. Police arrested one of two suspects when they returned for the fake money.

Their cache reveals glimpses into how counterfeiters operate — and how business owners and consumers can protect themselves from becoming victims.

The bills were produced on standard ink-jet printers loaded with resume paper that feels somewhat close to real currency.

"It's desktop publishing," Dalton says. "We call it ink-jet technology. It's readily accessible and it's not sophisticated."

On some of the confiscated copies, the back of the fake bill was upside down.

"That's called a practice bill," Mak says.

Others had $20 or $100 faces, but no backs on them yet.

Once counterfeiters get the backs and fronts lined up just right, they typically cut them, crinkle them a bit and prepare to pass them.

Many of the seized bills had the same serial numbers on them, and the resume paper was a bit more textured than a legitimate bill.

They are not detectable by the pens earlier used to check a bill's authenticity, Mak says.

"Those pens literally are worthless," Mak says.

But a search for the watermark — such as Jackson's ghostly image — reveals them as frauds.

"People may not take the time to look at it," he says. "Generally, if it doesn't look right or feel right, it isn't right."

The cases flow into the Medford Police Department daily.

As Mak inspected the recently seized bills Tuesday in the department's property room, three more cases came over the transom after U.S. Bank clerks discovered them in two separate deposits, one from Target and the other from Costco.

Medford police clear about two-thirds of their counterfeiting cases, usually after the bills are passed to alert clerks, George says.

Most counterfeiters feign ignorance, acting as if they were a duped consumer who got the bill as change in a past transaction.

"That's often their story," George says. "That's when we ask, 'How many more of those do you have in your wallet?' "

In Saturday's case, investigators don't know where or how much of the counterfeit cash was flushed into the system before the motel workers' discovery.

But police have a pretty good idea that some of it went from one alleged criminal to another.

"We honestly think they were actually out buying drugs with the counterfeits," Mak says.

Investigators found two pounds of marijuana, worth about $2,000, in one of the suspects' vehicles, Mak says.

"Somewhere there's a marijuana dealer with $2,000 in counterfeit money," Mak says.

Reach reporter Mark Freeman at 541-776-4470 or