Most of the reminiscing at the Pro Football Hall of Fame here has been about a onetime quarterback in the Pittsburgh Steelers' training camp who was thought to be a slow learner.

In 1955, John Unitas, a slightly stooped descendant of Lithuanian stock from the Mount Washington section of Pittsburgh, was drafted on the ninth round from the University of Louisville. Underscoring a confidence gap, the Steelers selected another quarterback two rounds later, Vic Eaton of Missouri.

Their prospects were dim because Ted Marchibroda was a two-season veteran who had been Pittsburgh's No. 1 draftee in 1953. Also returning was Jim Finks, 12th-round selection for the 1949 season.

Marchibroda now coaches the Balitmore Colts and Finks is general manager of the Chicago Bears.

There were 33-man squads in those days, so most clubs carried a maximum of three quarterbacks, Marchibroda and Finks got the most attention in training camp at St. Bonaventure College in Olean, N.Y., and the use of the most receivers.

Unitas found himself throwing to club owner Art Rooney's teen-age twin sons, Patrick and John. When they tried, he threw to "fat kids, tall kids, or anyone else willing," as Art Rooney Jr., now Steeler vice president, recalls.

Another son, Tim, wrote an 11-page letter, on both sides, to his father, saying "John Unitas is the best quarterback in camp."

Patriarch Rooney, a prominent horseman, answered by postcard from Aqueduct race track: "Don't be a wise guy. I pay my coaches a lot of money to make those decisions."

At cutdown time, after Unitas had sat on the bench for five exhibition games, Coach Walt Kiesling kept Eaton because he also punted and played some defense. Kiesling was aware of Unitas' strong arm, but was dubious about his mental capacity. Unitas was waived.

Jobs were scarce then because there were only 12 clubs in the National Football League. Unitas was dropped while the team was in Portland, Ore., so he cashed in his ticket home and thumbed his way back to Pittsburgh.

Already married, he took a construction job at $125 a week and played football on Sundays for $6 a game on a rubbled field under the Bloomfield Bridge for the Bloomfield Rams.

In 1956, the Colts needed a quarterback and General Manager Don Kellett gave root to a legend when he obtained Unitas with an 85-cent telephone call. Unitas still might not have made it to the Hall of Fame today if it hadn't been for an injury to regular Colt's quarterback George Shaw.

When Unitas reached the peak of his glory, in a sudden-death victory over the New York Giants for the NFL championship of 1958, he was referred to in Pittsburgh as the Steelers' "million-dollar mistake."

Kiesling made a feeble effort to justify his error by pointing out that all the rest of the NFL clubs had waived Unitas after the Steelers did.

Unitas later heard about Tim Rooney's letter. "Those Rooney kids had more sense than the coaches," he observed.

A resulting irony was that Unitas became known as a superb tactician and strategist. When former Giant middle linebacker Sam Huff joined the Redskins and called their defensive signals, he once remarked, "No matter what I try against Unitas, he beats me with his calls."

A hardscrabble guy, Unitas took compliments with the same stoicism with which he absorbed punishment. After a game in which he humilitated Green Bay's pass defense, Coach Vince Lombardi told reporters, "Unitas was the best quarterback I ever saw today."

When the comment was relayed to Unitas, he said, "That and a nickel will buy me a cup of coffee."

Before the extra period of the sudden death against the Giants, referee Ron Gibbs, an emotional fellow, approached Unitas and said, "John, I don't know whether you realize that this is precedent-setting...historical, do you realize the signifance of this game?"

Impatient to get going, Unitas said, "Stuff it. Give us the ball and let's get started."

In 1969, the Hall of Fame celebrated the league's first 50 years by selecting an all-time team, and Unitas was picked as best player as well as best quarterback.

Only the progress of Terry Bradshaw has helped Pittsburgh fans forget some of their regrets about underrating Unitas' mental grasp of the game.

Dick Butkus, former Bear middle linebacker inducted into the Hall of Fame today, said one of his fondest memories is catching a pass for a point after touchdown to beat the Redskins in 1971.

A small consensus here thinks George Allen would have landed Ken Stabler from the Raiders, if Allen were still coach of the Redskins. How he would have compensated the Raiders was not resolved, but it was remembered that Allen gave up two No. 1 draft choices for defensive tackle Dave Butz.

Maxie Baughan of the Baltimore Colts staff predicts Bill Kilmer or George Allen will be back in action before this season ends.