As the publisher of Nostalgia Press, he pioneered the reprinting of vintage comic strips in quality hardcovers and trade paperbacks.

As an editor and art director for two-and-a-half decades at Topps Chewing Gum, he introduced many innovations in trading cards and humor products.

Those were just the two that I remember, Bazooka Joe and Popsicle Pete, because they were cartoon characters, but the studio produced a lot of stuff, basic product artwork for advertisements.

[1] From 1953 to the late 1970s, Gelman headed Topps's Product Development Department, working with a staff that included associate creative director Len Brown, gagwriter Stan Hart, visual concept creator Larry Reilly, writer-cartoonists Art Spiegelman and Bhob Stewart, and designer-cartoonist Rick Varesi.

Gelman assigned work to numerous freelance cartoonists, including Jack Davis, Mort Drucker, Jay Lynch, Bob Powell, John Severin, Tom Sutton, Basil Wolverton and Wally Wood.

Beginning in 1967, Gelman supervised Wacky Packages, one of the biggest fads of the 1970s, and he was responsible for devising many other Topps cards, stickers, posters and humor products over decades.

The line includes The Secret of Crazy Cavern (1955), Riddle of the Sunken Ship (1955), Castle of Curious Creatures (1956) and Mystery of the Marble Face (1956).

After doing a facsimile reprint of the 1945 Little Nemo in Slumberland softcover, with an August Derleth introduction, Gelman began Nostalgia Press in the early 1960s.

Nostalgia Press editors Ron Barlow and Bhob Stewart, along with EC publisher Bill Gaines, selected 23 stories, one previously unpublished, for the full-color EC Horror Comics of the 1950s; with introductions by Stewart and Larry Stark, this oversize (10" x 14") hardcover was published by Nostalgia Press in 1971.

During the 1970s, he also published his Golden Age of the Comics series, reprinting such strips as Mandrake the Magician, Terry and the Pirates and Thimble Theatre.

The screenplay by Jules Feiffer was based directly on Thimble Theatre Starring Popeye the Sailor, a hardcover reprint collection of 1936-37 Segar strips published in 1971 by Nostalgia Press.

Gelman, who lived in Malverne, Long Island, maintained a collection of rare American and European periodicals dating back to the 19th century.