When Carl Gibbs finishes his regular work week as a criminal investigator for death penalty cases, the 69-year-old puts on his black suit, grabs his fancy derby hat and heads to his part-time job.

On most summer weekends, Gibbs can be found at Golden Gate Park wearing his “Monopoly man” outfit and calling balls and strikes for a bunch of middle-aged guys playing baseball by a rulebook last used in 1886.

Gibbs isn’t an umpire, but a “sir,” the original title of the uniformed men officiating America’s pastime.

Players doff their caps when they see him, treat him with the utmost respect and invite him out for beers after — and sometimes during — a long day at the yard.

This is the Bay Area Vintage Base Ball League, and it’s here that Gibbs fell in love with his new hobby and his new friends.

“I had no idea what I was getting into when I was invited 13 years ago,” says Gibbs, who lives in Berkeley but commutes to San Francisco for games. “I got on BART, and I’m riding in on a Sunday morning dressed like it’s 1886.”

When he walked onto the park’s Big Rec Field and saw a bunch of men wearing wool uniforms that looked to be a century old, he knew he was in the right place.

“The great thing about this league is it’s a competitive team sport without the alpha male element,” Gibbs says. “I think of it as 20% Renaissance fair, 80% Little League.”

Trying to find an adult sports league that suits folks who want a competitive environment without the toxicity often created by guys who take it way, way too seriously is what led a large majority of the players to the vintage league, which plays in cities from Dublin to San Jose.

Here, baseball is still baseball, but the funky rules which, oddly enough, date back to a time when the game was played with ruthless vigor, have somehow inspired a culture that promotes sportsmanship and respect over everything else.

Hit a ball nicely into the gap, and the other team’s shortstop is likely to come smack you on the rear and tell you “great hit” when you get to second base.

But most players don’t know each other’s real names; only their nicknames, given to them by their teammates.

There’s “Blaze,” the guy so fast and so good he nearly broke the league, before he moved away during the pandemic. There’s “Rocky,” perhaps the best pitcher to ever play in the league, who threw in the high 80s with a wipeout slider.

“I think he was drafted by the Phillies,” says Dave “Driver” Phillips.

There’s “SwitchBlade” and “Tools,” a pair of players who can play any position and do everything well.

Some nicknames have nothing to do with talent. “Shadow,” for example, shows up late, leaves early, and nobody knows where he goes.

The pitcher is called a “hurler” and sometimes throws between 150 to 200 pitches per game.

This league seems to have solved modern baseball’s problem with slow-moving play: Batters can’t call time. Quick pitches (a pitch thrown directly after receiving the ball back from the catcher) are allowed. There are no balks, and the ball is live, which means the hidden ball trick happens regularly.

“There are at least one or two a game,” says “Driver.”

Three strikes, and you’re out, but there are no foul balls, and tipped balls that are caught by the catcher are outs. There are seven balls to a walk, but if the pitcher plunks a batter, there’s no free base given; it’s just called a ball.

And once a ball is in play, look out.

Because the bats are so big and heavy — 35 inches and 40 ounces — and the ball is a smaller, softer ball than those used today, there are rarely home runs. Groundballs and fly balls are anything but routine, as players don’t wield modern-day baseball gloves, but tiny little leather mitts akin to a gardening glove.

Look at any longtime player’s hands and you’ll find mostly crooked fingers.

And the players absolutely love it.

“When I found it, it was a really fresh change, because it was competitive, but everyone was so friendly with each other,” Driver says. “You could tell everyone liked and respected each other. A lot of the adult baseball leagues are guys trying to relive their high school and college days. That competitiveness is overkill. But here, respect is a big thing. Being a gentleman.”

Many of the longtime players have a favorite rule they think sums up the entire league: the “Gentleman’s Call.”

If the “sir” has a difficult decision to make and isn’t certain which way to go, he can request the “Gentleman’s Call,” which transfers the power to the players. Were you out or safe?

Players must be honest or risk having their reputation smeared during gossip hour after the game.