The dawn of the “event” crossover as a product came in the mid-1980s, first with Marvel’s first Secret Wars in 1984 and shortly thereafter with DC’s first full reboot, Crisis on Infinite Earths. Secret Wars was a blatant multimedia cash grab – Mattel, a toy company, licensed Marvel’s heroes for action figures on the condition that there was a story that would give kids an excuse to mash their toys together. That’s exactly what Marvel did, beaming a group of heroes and villains to BATTLEWORLD, putting them in new costumes, and making everyone fight. Some of the changes were long-term—Spider-Man’s black costume, which would eventually become Venom, debuted on the cover of Secret Wars #8, and things like that have a marked effect on collectability. “If there’s a really good cover, those will stand the test of time,” says Ali Mir of AnZ Comics. “It doesn’t matter what the storyline is; it still ends up going up in price.” Despite the quality of the interiors being iffy, the cover of this issue – with Spider-Man looking puzzled at his new black outfit – has pushed its value up into the three figure range.

But quality matters. Good stories are the ones that have legs in the collector’s market regardless of covers. Crisis on Infinite Earths is dense and beloved, in no small part because of comics legend George Perez putting out some of the best art of his career. “Something like that still sells really, really well,” says Mir. Crisis on Infinite Earths #7, with a crestfallen Superman weeping over the dead body of his cousin Kara, is one of the most iconic images in comics history, making graded issues worth upwards of $75.

The recent glut makes the hunt for quality even more important for gauging collectability. Something like Secret Empire, Marvel’s 2017 summer event that saw a Captain America heel turn (to be generous), is not well remembered and has largely been relegated to dollar bins. “It took me years to get rid of all the copies I had of that book,” Mir tells us, “because there was just no demand for it.” Spoilers for folks who haven’t read it: it’s bad, and even variant covers – of which there were approximately a billion – can be found in dollar bins around the world.

Look for events that were well received in the moment that are still generating interest a few years later. Something like Jonathan Hickman and team’s X-Men relaunch, House of X/Powers of X, which launched Marvel’s mutants back to the forefront of comic fans’ minds, has real staying power. Another sneaky pickup that Mir flagged for us: Devil’s Reign, a Daredevil event from a few years back. “That was another really well-written story that I think long term, especially when you get Daredevil: Born Again coming out on Disney+ that people are going to look back on [fondly].” The multimedia tie-in probably won’t hurt, either. 

Here are a few collector’s items you should keep an eye out for:

The Flash of Two Worlds

The first major reworking of continuity in comics history, the Flash of Earth-One (Barry Allen) meets his comic book hero inspiration (Golden Age Flash Jay Garrick) and discovers that he’s real and from a parallel Earth. Silver Age key comics aren’t usually cheap, but this one can be had for a few hundred dollars, so it’s relatively affordable.