The sign sits outside of a modest second-floor office in a business park at the front of a Mount Pleasant subdivision — “Wonderlic. Pinpoint Potential.”

Company legend has it that former Dallas Cowboys coach Tom Landry saw a similar sign as he was driving on the Edens Expressway north of Chicago in the mid-1970s.

Landry, pondering ways to better evaluate prospective NFL players, had read about the work of Al Wonderlic in the field of intelligence and aptitude testing. When he saw the “Wonderlic Testing” sign on a building, he pulled off the expressway and found Al in his backyard, tending to his garden.

“Tom Landry asked Al if he felt the test would work in pro sports,” said Al’s grandson, Charlie Wonderlic, a Mount Pleasant resident and CEO of Wonderlic Inc. “And 35 years later, it’s still being used across the board.”

Today, the Wonderlic Personnel Test is part of NFL lore, used by the National Football League at its annual combine to assess the intelligence of college players before the NFL Draft.

Every year, supposedly secret results of the 12-minute, 50-question test are leaked and the predictive value of the Wonderlic is debated.

For example, LSU defensive back Morris Claiborne reportedly scored a 4 this year (an average score is 21). Former Steelers quarterback Terry Bradshaw famously scored a 13; he went on to win four Super Bowls. Aaron Rodgers and Eli Manning, the last two QBs to win the Super Bowl, supposedly racked up impressive scores of 35 and 39, respectively. Former Bengals punter Pat McInally, a Harvard grad, reportedly is the only player to ever score a perfect 50.

“It’s not that hard,” said Furman cornerback Ryan Steed, a Mount Pleasant native who took the test at the combine last month. “A lot of it is common- sense questions that go back to your math skills from middle school or high school. It’s nothing like a test you would take in college.”

So what does it all mean? Charlie Wonderlic, who moved a branch of the company to the Charleston area three years ago, said the test results are another tool in the kit for NFL teams to use, alongside 40-yard dash times and bench-press numbers.

“What teams are looking for is extreme scores,” said Wonderlic, who has five employees in his Mount Pleasant offices, 100 in the company overall. “They are looking at the scores that are extremely high and extremely low. Football is an occupation like any other in that you do have to learn.”

A high Wonderlic score is not a guarantee of NFL success, any more than a 4.3 in the 40 means a receiver will be All-Pro.

“And just because a person doesn’t score well doesn’t mean they can’t succeed,” Charlie Wonderlic said. “It just means that if you draft them, you should be aware of that. There could be a learning disability or one of any number of things, but you can do something about that, if you know about it.”

For prospects, the Wonderlic has become another measurement to max out on, just like the vertical jump and the 3-cone drill.

Steed, who starred at Pinewood Prep before his All-America career at Furman, said he took a practice Wonderlic test once a week during his pre-combine training.

“You want to take every step in the process like it’s the most important part of the process,” said Steed, projected as a middle-to late-round pick. “At the end of the day, the combine is a job interview. You’ve got to take it seriously and do your best on everything.”

Despite his training, Steed said he scored better when he took the test as a college junior (33) than he did at the combine (26).

“They take your best score, so that’s good for me,” he said.

Charlie Wonderlic said only he and one other employee know the actual scores.

“I can’t even share those with my family,” he said. “My boys, they are football fans and they want to know, my friends want to know. Half the scores I see reported are wrong.”

When Eldon F. “Al” Wonderlic — the name is an Americanized version of the German “Wunderlich” — invented his test in 1936, he had no idea of its NFL destiny.

Al’s grandson, Charlie, likewise had little idea he would one day run the company that his father and uncle also worked for. Charlie first went into international banking, working in London and South Africa, before returning to the family business 26 years ago.

“Growing up, I really didn’t understand how powerful the brand had become, and how brilliant Al was,” he said. “He had this recipe — measure something that’s very important, demonstrate how it relates to performance, overdo the research so that it’s impeccable, and yet make it really easy for users. That’s been our model ever since.”

Charlie Wonderlic decided three years ago to move his family to the Lowcountry, and opened a Wonderic office first on Daniel Island and now in Mount Pleasant. The company’s accounting functions are run out of the local office, but the CEO has plans for local expansion.

“We’re planning to grow in the area,” he said. “We’re looking at acquiring businesses that fit with us, and getting into working with local schools to measure learning outcomes. We hope that’s a growth area for us.”

Wonderlic’s association with the NFL hasn’t hurt, either.

“The test is administered two to three million times a year,” Charlie Wonderlic said. “But if you are not in hiring or education, you might not have heard of it. The NFL has bridged that gap for us. Every year, there are stories about the Wonderlic, and it’s made the general public much more aware of the name.”