Ever since the announcement of Metal Slug: Super Vehicle-001 in 1995, the Metal Slug franchise has been featured in dozens of magazines, guidebooks and manuals throughout the years.
As an effort to find all of the unreleased stuff out there, I started collectionning various Japanese magazines and a few PDFs found online. So here is all of the content I've found up until this day!

For easier exploration, I organized the info by which game they are talking about.