The entire run of Showcase (with the exception of some very random non-hero stuff) has been heating up, with these early Silver Age books containing plenty of key appearances.
Also on the Hot 100:
Several of the series appears on our Hot 100 list, and while many of them have already become quite expensive, the first Silver Age Atom appearance seems under-priced at the moment.
It's a pretty tough book to find in higher grade, but be patient and the right book will come along in time.
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