LET'S CALL THIS column "A Tale of Two Receipts."

It stars hometown public servants Todd Bernstein, founder of the Martin Luther King Day of Service, and Brett Mandel, Philly's ubiquitous good-government advocate.

In supporting roles are ticket writers with the Philadelphia Parking Authority and hearing examiners at the Parking Bureau of Administrative Adjudication.

Our story begins last June, when Bernstein, while in Manayunk for an arts festival, parked his car on Cresson Street, which restricts nonresidents to one hour of parking.

After 55 minutes, Bernstein retrieved the car then spent 15 minutes searching for a new spot. He spied one on the same block of Cresson, five cars from his original space, and parked.

Fifty-five minutes later, he found a $26 overtime ticket on his windshield. He was puzzled, because he'd moved his car from its original spot. He assumed that the one-hour ticketing clock started anew if he parked in a new spot.

"You should have parked across the street," the PPA ticket-writer allegedly said, when Bernstein tracked him down to ask about the violation.

"But there are no signs that say that," said Bernstein. "How are we supposed to know?"

The officer had no answer. Nor did a passing Philly cop, who'd never heard of the rule either.

Bernstein appealed the ticket and asked the hearing examiner, "How was I supposed to know of this rule?"

"You could go to the library or the PPA website," Bernstein said he was told, as if that's what most drivers do after they've left their cars.

The hearing examiner upheld the ticket, so Bernstein requested a second appeal. This time, a different examiner asked if Bernstein had any kind of receipt - maybe from a restaurant? - that would support Bernstein's argument that he had parked his car, moved it, then reparked it.

"Showing a receipt wouldn't prove a thing," Bernstein said, since a receipt from, say, a coffee shop would indicate nothing about his car's whereabouts as he sipped.

The point was lost on the examiner, who upheld the violation. Bernstein requested a hearing in Municipal Court but balked at the nonrefundable filing fee of $189. So he paid the ticket.

Who knew that a receipt - apparently any old receipt - might have helped him out?

Which brings us to Brett Mandel.

On the morning of last Dec. 6, he drove to the 1900 block of Green Street, which has a two-hour parking limit for nonresidents like him. Along for the ride was a friend who, with Mandel, attended a meeting at the nearby Julia R. Masterman School from about 9 to 10 a.m. Afterward, Mandel drove back with his friend to Fitler Square.

A few weeks later, he received a mailed notice from the PPA. It said that he failed to pay an overtime violation from Green Street that had been written at 12:30 p.m. the day of the Masterman meeting.

"I was nowhere near Green Street at 12:30," said Mandel.

He requested a hearing and presented a letter from the friend who'd attended the Masterman meeting with him, stating that they'd left the block by 10 a.m.

The hearing examiner pooh-poohed it. Instead, he wondered if Mandel had something to prove that he wasn't in the neighborhood at 12:30. Maybe a lunch receipt?

"But how would that prove my car wasn't on Green Street?" Mandel says he asked. "It would only prove that I wasn't on Green Street."

The hearing examiner upheld the ticket. So Mandel remains on the hook for $26, all because he didn't have a receipt - from someplace, for something - to wave around like it meant something.

In Bernstein's case, know what's funny? He was actually in the wrong about his ticket. According to PPA spokesman Marty O'Rourke, the one-hour limit on Cresson Street restricts a nonresident to one hour of parking, total, on a single block, no matter what side the car is on. If he moves his car to any part of the same block, the clock doesn't restart. It picks up where it left off.

So if a driver is unlucky enough to park where a PPA agent is keeping close tabs, he'll get a ticket.

When Bernstein contacted PPA ombudsman Sue Cornell to complain that none of this information is on the PPA website, she emailed back that she was updating PPA's website and Facebook page to make parking rules clearer.

That was five months ago, but the sites are still murky.

Until conditions improve, I suggest we save our receipts, no matter what they're for - blood work at Jefferson, crab fries at Chickie's & Pete's - since they might prove useful some day. I also feel obliged to note that the Internet abounds with websites that offer, for a fee, to produce phony receipts (although "not for any illegal purposes," warns SalesReceiptStore.com).

I might give them a look. Because some parking spots are just too tight to get out of.

Contact Ronnie at polaner@phillynews.com or 215-854-2217. Blog: philly.com/ronnieblog. Twitter: @RonniePhilly.