Jughead’s Time Police was a six-issue series where Archie’s friend Jughead travels through time with Archie’s distant descendant January McAndrews, who works for the Time Police. “Will the Real Colonel Pickens Please Stand Up?” appears in Jughead’s Time Police 5 (March 1991), and on the opening page Jug is in the library researching the American Civil War.
Of course he’s not actually “pouring” over the books, which is a terrible thing to do in a library. He’s poring.
In one of the books he sees a daguerreotype (also misspelled, but helpfully defined in a footnote in the comic) taken in the war that he appears in, and the adventure begins.
“Will the Real Colonel Pickens Please Stand Up?” was written by Rich Margopoulos, pencilled by Gene Colan, inked by Rudy Lapick, lettered by Bill Yoshida and coloured by Barry Grossman. I read it in the collected edition Jughead’s Time Police (ISBN 978-1-68255-913-0), published in 2018. It is copyright Archie Comic Publications.