If you've spent any time riffling through the used vinyl bins at Seattle record stores, you've probably spotted the name Nick Johnson written boldly on the covers of jazz and avant-garde titles. It turns up a lot. Some might view the signature as an egocentric form of vandalism, but serious fans of these genres know better—the name Nick Johnson has come to represent the stamp of quality. And bonus information: In addition to his name, Johnson also had a habit of annotating his records with addenda—release date, song-by-song instrumental credits, etc.—that indicate the work of an obsessive historian. Or at least an obsessive. But if the scrawled signature, with its little squished infinity logo underneath, threatened to devalue the records for the resale market, the added facts and insights more than make up the difference. Seattle crate-diggers, heads, and beat makers have been scooping up Nick Johnson–signed LPs for years—I have two: Weather Report's self-titled 1971 album and Airto's Fingers—and wondering about the identity of the man behind the autograph.

So who is this Nick Johnson? He's a Seattle native now in his 70s and battling the debilities of old age: arthritis, bad back, hip-replacement surgery. He got seriously into music through his junior-high teacher, who brought to class R&B 78s by mostly obscure black groups like Hank Ballard and the Midnighters. That spurred Johnson to explore blues and jazz and start buying records. His father (whom Johnson calls "hokey") was a square-dance caller with a collection of his own, 78s by Benny Goodman and other mostly white swing bands. Johnson loved those, too. Then in the late '50s, he immersed himself in bebop, then newer jazz, abetted by the recordings of Norman Granz's Jazz at the Philharmonic concerts, which united older players with younger ones for jam sessions. His record collection mushroomed.

Johnson got his start in radio while a creative-writing major at the University of Washington. Lorenzo Milam had started the educational, noncommercial KRAB 107.7 FM in 1962 (you can learn more about the station at krab.fm). The next year, Milam was seeking spoken-word segments to put on the air, and Johnson volunteered to read his own short stories and "other such wig bubbles." At KRAB, he met Lowell Richards, who was hosting a jazz show. Richards took to borrowing Johnson's records—he'd already accumulated thousands. This led to Johnson getting his own late-night show. His on-air handle was Captain Baltic, a nickname a friend bestowed on him during a druggy bender in the '60s, and from the sound of it, his broadcasts were a trip, too. He called the program Bumbling with Baltic—Jazz and Other Eccentricities.

"The late-night show would get pretty far out," Johnson says. "It was pretty eclectic. I would play something from the '30s and then I would play Sun Ra or something like that, back-to-back. Lenny Bruce, Lord Buckley, we mixed it all up. I used to fill up a big box with 250 or 300 records and start playing stuff. 'Oh, this one makes me want to play that one, bang bang bang. Oh, I should throw on some blues after that.'"

The selections were all based on his own whims and taste. "Nobody told us what to play. [That sort of free-form philosophy] is kind of what ultimately did in KRAB. We had political shows, then we'd have Korean music, then jazz, then gospel. It jumped around so much. We had a lot of regular listeners, though. It was weird—after we went off the air, for several years I'd go down the street and I'd be talking to somebody and people would say, 'Oh, Captain Baltic!' They'd recognize my voice."

Johnson laments the conservatism and one-dimensionality of most modern radio stations. KRAB, he says, "survived for a long time on donations from the public and government grants and stuff, up until Nixon got into office and then the grants started trickling off. Every time the Republicans get into the White House, they chip more out of the budget."

After KRAB folded in 1984, Johnson hosted jazz shows on KSER (both were owned by Jack Straw) and helped out with KBCS and KUOW, all while working in the accounting department for various shipyards and then as an estimator for Boeing. Johnson's jazz fandom also extended to festivals; he produced New City New Jazz, the precursor to Earshot, in 1987.

Johnson got out of the jazz radio DJ game in the late '80s. "It wasn't a paying job," he explains. "Up until 10 years ago, I was working [a day job], so I'd be up late at night and have to get up to go to work... As you get older, that kind of lifestyle wears you out."

As it does to many record collectors, the time came when circumstances forced him to downsize. Johnson and his wife had been living in the same Queen Anne home for 43 years and their arthritis made using the stairs difficult. They wanted to move, but the huge collection needed to be culled before that could happen. So, in 2004, Johnson started selling off his most valuable items, beginning with the 10-inch records, then moving on to the 12-inch LPs. Eventually, about 5,000 pieces made their way to Easy Street's and other Seattle record stores' used bins. Don't worry—Johnson digitized everything onto four terabyte-capacity hard drives.

Johnson has never earned a penny for all his years working in radio, although he admits he did receive some free records and T-shirts—and he had the thrill of interviewing many of his heroes in the studio. But you sense he doesn't care about the lack of financial reward. His enthusiasm for the music is still infectious, in several senses. After years of enriching the collections of local heads, Johnson's castoffs have begun to show up in new mixes by enterprising DJs. The Nick Johnson EP, Vol. 1 is a collaboration between Seattle producer EarDr.Umz—aka Geoff C. Hartkopf—and his Tokyo-based partner T-Bone Steak, sourced mainly from records formerly owned by Johnson (they found them at Everyday Music and the now-closed Queen Anne branch of Easy Street Records from 2004 to 2013). The eight tracks recall the jaunty, sophisticated, jazz-inflected hiphop of artists like Madlib and Mr. Scruff, and the EP is available at eardrumzthemetrognome.bandcamp.com.

Vi Tranchemontagne, a buyer at Easy Street when Johnson began selling his collection, ended up purchasing nearly 200 of Johnson's treasures for himself. Tranchemontagne now hosts the weekly jazz brunch at Revolver Bar, one of the few such DJ events happening in Seattle. At the beginning of "Riff" on EarDr.Umz's EP, there's a recording of an Easy Street clerk saying, "For a while, our whole jazz section said 'Nick Johnson.'"

The infamous signature, which began as a way for Johnson to distinguish his records from those of the radio stations where he worked, has become a trademark, signifying a particular kind of life's work. It's also funny. Hartkopf spotted a "Nick Johnson" on Buddy Miles's teeth on We Got to Live Together and another emblazoned on a wiener on Lou Donaldson's Hot Dog. Hartkopf has more than 100 Nick Johnson records in his crates and he promises several more EPs bearing samples from them. He and T-Bone were "pretty much buying anything we saw with Nick's name on it, for a time. They just kept popping up. Everything we'd pull out that caught our eye, it would be a Nick Johnson record. This was weird—it was like he was following us. It was kind of an inside joke, and we kept going with it. Once [Queen Anne] Easy Street unfortunately closed its doors, we felt it was a good time to share it with everybody. We've got tons more that we can do. Hopefully, it'll come full circle and we can get the Nick Johnson EP on record."

For the record, Johnson thinks his namesake EP is "interesting." In an e-mail to Hartkopf, he wrote, "If my joints weren't so old and bad I'd probably be up dancing instead of sitting here tapping my feet and mentally swinging. The old days at KRAB were really an experience, and I'm grateful whenever someone does anything to revive the memory. Keep on doin' it, because you might get a new generation to dig this old stuff, albeit in a new way."