DC Price Logos
Superboy #94, January 1962 (https://www.comics.org/issue/16713/) was the first use of the "BLOCK 12 cent" DC logo to appear in the title. Superboy #93, December 1961 (https://www.comics.org/issue/16625/) is actually the first 12 cent cover price, but it uses an uncommon and rarely seen version of the 12 cent DC logo. Other variations of both the 10 cent and 12 cent logos are shown below, along with an ad for "Still 10 cents" from Showcase #35, December 1961 (https://www.comics.org/issue/16544/).
Information and scan from "Crazy Ed" Savitt, used by permission.