Given the ads for the Spartus Camera and the Hopalong Cassidy pocket knife, I'd guess some publisher bought/inherited/found in a dustbin a stack of Catholic Pictorial insides and slapped a cover on them (after selling a couple of ads). But another possibility occurs to me. Given the 5-cent sales price and the super-generic cover, might some less than scrupulous distributor have printed a slew of these covers and wrapped them around unsold returned comics which were supposed to have been destroyed? It'd be less obvious than selling comics with stripped titles. More effort involved, though, in putting on new covers.
Link to the book:
Lots 'O' Fun Comics