The listing on the crime memorabilia Web site Supernaught says it is “one of the few items that the Virginia killer Seung Hui Cho sold on eBay to raise money for the guns, clips and ammo utilized during the rampage.”

The calculator and hundreds of items like it — the personal effects, paintings, letters and even fingernails of killers — are being peddled to collectors by at least a half-dozen Web sites as “murderabilia.”

Seung Hui Cho’s calculator is also a rarity. Experts and murderabilia collectors say it is the first item with a connection to the gunman to be available for purchase in more than four years — since the first 48 hours after his mass murder. It is the only item of his on the market, experts say, at a time when Virginia Tech is back in national news after the December shooting death of a police officer in Blacksburg.

The market for murderabilia is hardly a new phenomenon. In London during the late 1880s, British subjects paid admission to stand in the rooms where Jack the Ripper slashed his victims.

In the 1950s, the Ford sedan driven by killer Ed Gein, who inspired the movie “Psycho,” was paraded around county fairs and promoted as “the car that hauled the dead from their graves.”

Murderabilia can command steep prices. The handgun Jack Ruby used to kill John F. Kennedy assassin Lee Harvey Oswald was sold in a 1991 auction to Anthony V. Pugliese III, a Florida real estate mogul, for $220,000. Paintings by executed serial killer John Wayne Gacy, who murdered at least 33 boys, have been purchased for as much as $15,000.

Today, most murderabilia is sold online, making the shopping for serial killer collectibles easier than ever.

“It’s an insidious and despicable industry,” said Andy Kahan, a Houston-based victims’ rights advocate and law enforcement official who has led a nationwide campaign to prohibit the sale of murderabilia.

Although eight states, including Texas and California, have laws that prohibit convicted killers from profiting from their crimes, efforts to push legislation through Congress have failed repeatedly. Virginia, Maryland and the District permit the sale of such items, Kahan said.

Over the years, Kahan has amassed a “smorgasbord of items,” including a lock of Charles Manson’s hair braided into the shape of a Nazi swastika, purchased for about $50, and fingernail clippings of killer Roy Norris, who is imprisoned in California for kidnapping, torturing and murdering teenage girls. The fingernails cost $12.99, which Kahan described as “a bargain.”

Kahan said he uses the murderabilia for testimony and lectures on how people profit off of “heinous and diabolical crimes.” Selling the items of killers, Kahan said, “gives them infamy and immortality they don’t deserve.”