The Sheehy brothers are baseball diehards.
Brian, a history teacher at North Andover High, has been on a diamond since he was 6.
And for the last decade or so, the 33-year-old Methuen native and his younger brother, Chris, have played a version that is true to the game's origin dating back 150 years: vintage baseball.
Brian started suiting up in 2002, while he was still in college.
"I was a history major, played and loved baseball just about all of my life, so the mixture of the two has been a perfect fit for me," said Sheehy.
These days, he is the president of the four-team Essex Base Ball Organization , based at Newbury's Spencer-Peirce-Little Farm. He's also captain of the league's "travel team," the Essex Base Ball Club, and plays for the league's Lowell Base Ball Nine, captained by 29-year-old Chris.
"I went to a game that my brother was playing in, and they happened to be short a player," said Chris Sheehy, who played high school ball at Central Catholic in Lawrence.
"So I played and really enjoyed it,'' he said. "It was fun and different, playing without a glove and some of the other weird rules, and also got me into learning more about the history of the game."
The Essex Base Ball Organization's other teams are the Newburyport Clamdiggers, the Portsmouth (N.H.) Rockinghams, and the Lynn Live Oaks. (The first African-American professional baseball player, Bud Fowler, played for the team's namesake Lynn Live Oaks in the 1870s, according to captain Mark Scapicchio.)
Other vintage squads across the region include the Mudville Base Ball Club in Holliston, the Boston Beaneaters, and the Bristol Blues Vintage Base Ball Club in Rhode Island.
Matches can be found locally on many summer weekends.
■ Next Sunday, July 5, the Hingham Historical Society will host a game at Talbot Field between the Coopers and the Derbys at 3 p.m. The Derbys have prevailed in eight of the last nine matchups against their rival, including a walk-off win last summer..
■ On July 18, Essex clubs will play at the Concord Museum in conjunction with its “Art of Baseball” exhibition.
■ On July 25, the Essex Base Ball Club will face the Cleveland Blues on George’s Island in Boston Harbor.
Ray Shaw was drawn to the simplicity and spirit after seeing his first vintage game more than a decade ago.
"Playing in the style of the 19th century, by the quirky old rules in old uniforms, is just counter to everything we know about the modern game," said the 70-year-old Westport resident, a member of the Bristol Blues.
"This is baseball the way it was meant to be played in the rough and tumble days of grind-it-out baseball, when men and boys played for the pure love of the game," added Shaw, who now participates as an umpire.
"There were no fences to boom home runs over. Every player has to earn his runs with strategy and base-running expertise. Fielders must earn their due with skill and daring. You won't find a vintage ball player who hasn't experienced the pain of a catching a hard-hit ball."
The games, say many players, definitely take on an atmosphere of “the more, the merrier.”
Lee Smith, a 45-year-old Concord resident who suits up for the Live Oaks, has been playing vintage ball for 11 years.
"I saw an ad for players and stumbled across a game one day. I liked what I saw, so I tried out and have been on the team ever since," he said.
"As a baseball fan it seemed like a great way to keep playing the game and honor its traditions," said Smith. "It's a really pure form of the game. I love the style of play and the rules. Plus, it enables old guys like me to keep playing."
Today's vintage games undoubtedly look strikingly similar to the June 12, 1880, matchup between the Worcester Ruby Legs and the Cleveland Blues at the Worcester Agricultural Fairgrounds, when the host team's John Lee Richmond fired baseball's first recorded perfect game.
"I like the fact that you can see the evolution of the game through watching us play," said Brian Sheehy.
Essex teams play by the "Abridged 1864 rules." The pitcher stands 45 feet from home plate, and must deliver the ball underhanded.
"You can't overrun first, you have to get back to your base on a foul ball, a ball caught on one bounce is still an out, if a ball's first bounce is fair it's fair for good, et cetera," said Scapicchio, 54, a Melrose native. "You really have to change your instincts from the baseball you played growing up."
One of the enduring attractions of baseball, including the vintage game, is that it doubles as a fountain of youth. But there's often a price. Scapicchio admitted, "It usually takes me until Wednesday to rebound from a Sunday doubleheader."
"The level of play is both an attraction and a challenge," said 54-year-old Ralph Hebb of Waltham. "I've become a much better player over 10 years of vintage ball than I ever did over 20-plus years of softball, simply from having to keep up with the other players. The most obvious tangible difference and challenge is the lack of gloves."
The appeal of the vintage game ebbs and flows. In the past decade, teams have sprung up and faded away. Shaw said he hopes to form a vintage squad in the Dartmouth area, with a game planned for August at the Buzzards Bay Brewing Co. in Westport.
"What I love about the vintage game, and what local recreation departments should love about the game, is that it doesn't require manicured fields with chain-link fences, backstops, scoreboards, dugouts, and lights," said Shaw.
"Just one open field with one bat and one ball makes a perfect venue for vintage baseball. Simple, straightforward, and fun to watch and play," Shaw said.
For more details on the Essex Base Ball Club, including a schedule of games, visit www.essexbaseball.wordpress.com.