Buy out an entire district's worth of Action Comics #1, put them in a time capsule in the backyard of my present day property with a forged note saying they are from my great-great-grandfather who saw the value in the art form and wanted to literally turn his pennies into pounds.
Add a few other knick-knacks from the time period to authenticate it, maybe a photo of myself dressed as an older person.
Obviously, if I bring back a pristine copy that was chronologically printed the day before, it'll be considered a fraud, but 100 copies with obvious degredation, yet still air tight, would show as originals.
Oh, and probably buy the other comics on offer for the hell of it. Only buying copies that would otherwise be thrown out, else someone who was meant to read an issue would miss out and we don't want shenanigans.