A 3-foot-long ramp invented in the 1930s could have more say about who wins the U.S. Open come Sunday than all the swing coaches, sports psychologists and fitness gurus in the wide world of golf combined.

It's called a "Stimpmeter" in honor of inventor Edward S. Stimpson and in a nice bit of serendipity, the device traces its origins back to storied Oakmont Country Club, site of this season's second major. No matter how much golfers bellyache during the week, the ramp, slightly less than 2 inches wide, will have the last word on how fast the greens are running.

Before play begins Thursday morning, and then again at the end of each round, a U.S. Golf Association official in charge of course set-up brings the Stimpmeter and three golf balls onto a green. He puts each ball in a notch at the top of the ramp — slowly raised to a 20-degree angle — and lets them roll down and run out on the flattest section of the putting surface. He then repeats the process from a notch halfway down the ramp, mostly as a backup test, then walks to the other end of that flat section and rolls the balls in the opposite direction.

The number of feet the ball rolls from the top of the ramp becomes it's Stimp rating, so that a "10.5" — the recommended speed for greens at U.S. Open — means the three balls averaged a distance of 10.5 feet.

But even USGA executive director Mike Davis acknowledged Wednesday that the putting surfaces on Oakmont's punishing layout more likely will be dialed up to the 13-15 range. Contrast that with green speeds at your local muni, where an 8.5 Stimp rating would be considered lightning-fast.

"They're never going to get them exactly the same, because even the USGA can't control the weather," former Open champion Rory McIlroy said.

"But if they were as inconsistent as they must have been back in the day," he chuckled, "can you imagine how much more complaining there'd be?"

The maddening inconsistency of the greens some 80 years ago is what prompted Stimpson, a Massachusetts state amateur champion and Harvard golf team captain, to produce a prototype in 1936. By most accounts, he read about how Gene Sarazen, already a two-time U.S. Open champion and Stimpson's favorite player, putted a ball off the green and into a bunker during the 1936 Open at Oakmont and became determined to come up with a uniform measurement for rating greens.

His son told the Boston Glove in 2007 that his father had been working on the problem since at least 1926, when the elder Stimpson missed a putt inside 2 feet in the 1926 New England Amateur. Stimpson often brought various iterations of the device — all made from wood — along to courses he was playing and invited club officials to try it out.

Remarkably, it didn't gain full acceptance for decades, despite Stimpson's unstinting efforts both in person and in published papers. The USGA gave the device a once-over at the 1963 U.S. Open at The Country Club near Boston, where Stimpson was a member. The USGA's Frank Thomas designed an aluminum version with slight modifications, painted it green, and put it into official use in time for the 1978 U.S. Open at Cherry Hills. The only modification since is switching colors from green to blue.

Not all golfers believe the Stimpmeter makes that much difference. Brandt Snedeker thinks the variances are still great enough between greens that a golfer's instinctive "feel" for the speed is the only thing that matters. Tech-minded Phil Mickelson thinks it isn't precise enough.

When his putting coach, former NASA scientist Dave Pelz, came up with a device called the "Pelzmeter" in 2007, some fellow golfers asked whether it was worth the effort.

"Oh, yeah," came Mickelson's mocking reply. "I'd much rather use a stick that was invented 71 years ago. Twenty years before NASA? That's great."

Two-time U.S. Open champ Ernie Els has a foot in both camps.

"I remember when you tried out a club on the range and if the ball went straight, you put it in play that day. Guys are so dialed in today, with equipment and everything, that every little bit of information helps.

"But when you're standing over a 10-footer down a slope with a tournament on the line," he said finally, "I'm not sure knowing the number for how fast it's supposed to run is going to do you much good."