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 !!!

Topps added several interesting cards in 1973 starting with card #1, a special card honoring the All-Time Home Run Leaders. Also new was the All-Time All-Star subset featuring Babe Ruth, Ty Cobb, Lou Gehrig and other all-time greats on their own special cards.

TOP ROOKIES were Mike Schmidt, the Phillies super-star Hall-of-Famer and the White Sox relief pitcher Goose Gossage.