Professional slow - pitch softball came to the Washington area yesterday, offering the somewhat alien sight of a masked pitcher throwing to an unmasked catcher. It also provided more outstanding fielding plays in one afternoon than the average baseball hibitue can expect to see in one afternoon than the average baseball hibitue can expect to see in a season.

With a 12 - inch softball rocketing off the bats and with the bases only 65 feet apart, it almost took an exceptional defensive play to record each out.

In addition, large leads are no guarantee of victory, as the Bowie - based Baltimore Monuments discovered. Breezing along with a 9 - 1 lead after two innings and taking a 17 - 12 edge into the climactic seventh, the Monuments dropped an 18 - 17 decision to Milwaukee Copper Hearth in the opener of a doubleheader at Rip's Memorial Field.

A 10 - run fourth inning helped the Monuments capture the second game, 15 - 10.

It was, as Bowie Mayor Audrey Scott nited during pregame ceremonies, 'a historic moment.' This was the inaugural for the American Professional Slo - PItch League, with the other 10 teams waiting until last night to start.

So the first ball, after a bounce across the plate, was retired for posterity and the Monuments' Bill Brantley, after whacking the first home run over the 300 - foot fences, was presented a trophy when he reached the plate.

Home runs were not a rare item, with 11 featuring the first game. That included one by Malwaukee's Derek Gallagher that bounced over an out - fielder's head.

In the second game, however, a strong wind blew in toward the plate and limited the home runs to one.

The crowd of 3, 300 was somewhat subdued in these blue - collar surroundings where the concession stands sold draft beer.

To the Milwaukee team, public - ad - dress announcer Charlie Eckman said, 'I think you'll enjoy Bali - mer. Our beer is just as good as yours.'

The visitors stumbled at the beginning, George Kelepouris and Ken Tricker tripping over the dugout steps during the introductions. And pitcher Ken Parker was rattled by Monument manager Ray Duncan, who innisisted loudly to the umpires that 'he has to throw with a three-foot arc. If you don't do something, the man's going to make e a mockery of this game.'

But Tom Gorski relieved and hit a couple of homers bessides muffling the Monument bats a bit. James Dillard whacked two homers and two triples for the visitors, who eventually solved the arcing deliveries of masked 'Lord' Byron Zeigler.

Zeigler had his nose flattened in a recent game and it was easy to see why. What wasn't so simple was figuring out Duncan's frequent visits to the mound when Zeigler was in trouble. After all, how can you advise a slow - pitch pitcher whose offerings are being belted in every direction?

Jim Ports, the Monument general manager, was not unhappy with the opening crowd, although he had hoped to fill all 5,000 seats.The switch to night games beginning with a 7:30 doubleheader ag4ainst Milwaukee tonight, could help.