I’m curious about the use of the word “laser” here. The description says the comic is from 1939 but the laser wouldn’t be invented until the 1960s. And the word “laser” is a really specific acronym (Light Amplification by Stimulated Emission of Radiation) that doesn’t seem be appear in sci fi before then (There were heat rays and blasters but no lasers from what I can tell).
The date after the series title indicates when the series started, not the publication date of the actual panel. It's there to clarify that it's in the 300th issue of the original run, not the current one, or any of the ones that came between.