The cards in this 587-card set measure 2 1/2" by 3 1/2". In 1961, Topps returned to the vertical obverse format. Introduced for the first time were "League Leaders" (41-50) and separate, numbered checklist cards. Two number 463s exist: the Braves team card carrying that number was meant to be number 426. There are three versions of the second series checklist card number 98; the variations are distinguished by the color of the "CHECKLIST" headline on the front of the card, the color of the printing of the card number on the bottom of the reverse, and the presence of the copyright notice running vertically on the card back. There are two groups of managers (131-139/219-226) as well as separate subsets of World Series cards (306-313), Baseball Thrills (401-410), MVP's of the 1950's (AL 471-478/NL 479-486) and Sporting News All-Stars (566-589). The usual last series scarcity (523-589) exists. Some collectors believe that 61 high numbers are the toughest of all the Topps hi series numbers. The set actually totals 587 cards since numbers 587 and 588 were never issued. These card advertising promos have been seen: Dan Dobbek/Russ Nixon/60 NL Pitching Leaders on the front along with an ad and Roger Maris on the back.Other strips feature Jack Kralick/Dick Stigman/Joe Christopher; Ed Roebuck/Bob Schmidt/Zoilo Versalles; Lindy (McDaniel) Shows Larry (Jackson)/John Blanchard/Johnny Kucks. Cards were issued in one-card penny packs, five-card nickel packs, 10 cent cello packs (which came 36 to a box) and 36-card rack packs which cost 29 cents. The one card packs came 120 to a box. The key Rookie Cards in this set are Juan Marichal, Ron Santo and Billy Williams.