Neat oddball set with a very unusual mix of players. A promotional lead-in for "Cardboard Dreams" a soon to be sportscard magazine. Promo cards were given out at a few regional baseball card shows mostly in So. Cal.
MLB filed lawsuits against similar magazines and the magazine was cancelled before 1st issue leaving just a small run of promo cards (limited to 5,000) and some scarce proofs.

      SERIES 1                   SERIES 2
  #1 Willie Mays            # 9 Mickey Mantle                
  #2 Nolan Ryan             #10 Nolan Ryan & Sandy Koufax   
  #3 Tony Gwynn             #11 Frank Thomas & David Justice
  #4 Wayne Gretzky          #12 Brett Hull                  
  #5 Jose Canseco/Madonna   #13 Ted Williams & Joe DiMaggio 
  #6 Ken Griffey Jr         #14 Barry Sanders               
  #7 Bo Jackson             #15 Dan Marino                  
  #8 Michael Jordan         #16 Magic Johnson & Larry Bird  

 Prototype #1: Nolan Ryan / Wayne Gretzky / Bo Jackson / Jose Canseco & Madonna
 Prototype #2: Mickey Mantle / Nolan Ryan & Sandy Koufax 
               Ted Williams & Joe DiMaggio / David Justice & Frank Thomas

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 !!!