The date you quote (1948) is the date the publisher applied for a Second Class Mailing permit. Further down the indicia it says "Entire contents copyright 1956 by Feature Publications," and under panel three "November-December, 1956." Giolitti was well-established by then.
Thanks for the link to the biographical info on Galindo. Be assured that I'm not putting him down for swiping. My days of being a firebrand Adkins-hunter are long over. Galindo showed influences from Raymond and from Ruben Moreira among others. The guy had great taste.
Link to the book:
Prize Comics Western 119