1952 is often thought of as Topps 1st baseball card set, but it was not.
Topps issued several smaller baseball card sets prior to their huge 1952 set.
The buzz word at Topps back then was "BIGGER is BETTER" for their 1952 Topps set which Topps described as: "GIANT IN BOTH SIZE and NUMBER of CARDS" (407).

Key card in the 1952 Topps set is #311 MICKEY MANTLE. Often called Mickey Mantle's Rookie card - BUT IT IS NOT. That honor goes to his 1951 Bowman.
1952 Topps "High Numbers" (#311-#407), are very, very scarce with an interesting story:
This HUGE set was released in series, released weeks apart. By the last series, baseball was over and football starting.
??? Perhaps the set was too huge ???
Shops had cards left from earlier in the year so many orders were cancelled, thus the scarcity.

Adding interest is how Topps got rid of the now useless cards, including THOUSANDS of MICKEY MANTLE's. They dumped them into the Ocean !!!

Without a doubt my FAVORITE SET - PERIOD. Regular issue, test issues, inserts ... whatever ... this is # 1 !!!

Similar to the early 1900's Mecca Double Folders, these colorful 2-1/16" x 4-7/8" cards are actually 2-cards-in-1 ! Perforated in the center, you can fold to create cards of 2 different players. Unperforated 1955 Topps DoubleHeaders exist. All 132 players (66 cards) in the 1955 Topps DoubleHeaders set were also in the regular 1955 Topps set, with the same action image.
NOTE: Laid side-by-side the cards form spectacular scenes from actual stadiums !!!
Old-timers - can you identify the stadiums ?

ROOKIES:
  Harmon Killebrew, Hal Newhouser
STARS:
  Ted Williams, Hank Aaron, Jackie Robinson ...