From his last few months at Marvel in 1970, this page from SILVER SURFER 18, the last issue of the series, and the only issue drawn by Kirby.

One of those random single-issue stories by Kirby that few people know about. Along with anthology mystery stories in CHAMBER OF DARKNESS 4 and 5,
And a brief series of 10-page Inhumans stories in AMAZING ADVENTURES 1-4, these were among the last few stories Kirby did for Marvel in 1970.

Possibly Kirby was experimenting with new characters other than the ones he normally worked on, or he was churning out pages to fill out his contract before departing over to DC. Since most of these stories he both wrote and pencilled, I suspect he wanted to do work himself that Stan Lee couldn't take credit for. Or possibly he was warming up for doing a ton of writer/artist work he'd soon be doing at DC, his first writer/artist work in 10 years. In any case, they're interesting stories, for being obscurities outside the work he is known for.