So good that at a Dec. 5 meet in Ambler, Mason, who is 5-foot-7 and a bantam at 155 pounds, won a national championship sponsored by the United States Powerlifting Federation.
He bench-pressed 1923/4 pounds.
He is modest about his accomplishment.
"It was in my age group - 75 and older - so I didn't have a lot of competition," he said with a chuckle.
Jan Shendow, secretary-treasurer of the power-lifting federation, called Mason's achievement "pretty good, very good, a record."
But Shendow said that people would be surprised at how many people older than 75 were competing.
"I don't have the figures, but it's probably somewhere between 20 and 50 across the country," he said.
In practice, Mason has bench-pressed up to 200 pounds, said Lance Jones, his trainer at the JCC Kaiserman gym.
"He's really amazing," Jones said.
At the gym Monday afternoon, Mason went through his usual routine: stretching out on his back on the bench, extending his arms up, lifting 135 pounds into the air, and then bringing the bar with the disks on either end down to his chest. He repeated the move three times.
Jones, who has been Mason's trainer for the last two years, "spotted" him - that is, stood by to make sure he did not lose his grip.
"That drops pretty fast and could crush him," Jones said.
Jones called Mason a great example not only to his peers but also to younger people.
"Kids 17 and 18 come in here to work out and see him doing these lifts and can't believe how old he is," Jones said.
"He's very strong."
A native of Philadelphia who now lives in Overbrook Park, Mason is a graphic artist and runs his own business from his home studio.
He served in the Army during World War II as a first lieutenant and was part of the forces that landed at Omaha Beach during the Normandy invasion.
He said he had always been good at sports, particularly baseball, tennis and golf - but turned to power lifting because his knees were giving out.
"Arthritis, I think," Mason said.
Six months ago, he had a knee replacement and was back in the gym shortly thereafter.
"The good thing about bench-pressing is you use just your upper body and give your legs a rest," Mason said.
He said he was encouraged by a fellow septuagenarian, Leo Ford, 71, a Russian immigrant who has been lifting weights since he was a young man. He works out with Mason sometimes.
"Got to give Leo the credit," Mason said.
Mason said he hoped that his activity was an example to his peers.
"No matter how old you are, you can do something," he said.
And, to keep his mind as well-honed as his body, Mason returned to college in 1991.
"Villanova had this great free program for seniors," Mason said.
He graduated magna cum laude with a degree in geography.
"So if you ever get lost, you can call me up, and I can tell you where you are," he said jokingly.
Mason said he also stayed in shape so that he could keep up with his wife of 53 years, Bobbi Helms, who runs 12 miles a week.
His son and daughter and four grandchildren also are encouraged to get moving.
"A lot of people exercise when they're young, then give it up when they get married and then find it hard to go back to when they're 40," Mason said.
Asked about his goals, he said: "I turn 80 in May and hope to compete in the 80-and-over group," he said.
"I think I'd have a good shot at winning."