One thing I can think of, Harvey maintained the Black Cat longer than any other character. They kept the original run going into the 1950's, with a lot of reprints. (Before changing the format to horror.) Then, in the early 1960's they did a few 25 cent issues of Black Cat reprints, or mostly so. Plus the Harvey family again published the character around 20 years ago.
Without research and firm legal advice, I'd be real careful with that character.