Pass all 7 Metal Slugs on Hard Difficulty / Limited Continues. Pass all 7 Metal Slugs on Normal Difficulty / Limited Continues.
Pass all 7 Metal Slugs on Easy Difficulty / Limited Continues. The character that you pass each game with does not matter. To unlock these features, you must pass all 7 Metal Slugs on limited continues, varying through all the difficulty levels. Metal Slug 2, Metal Slug X, Metal Slug 3, Metal Slug 4, and Metal Slug 5. Unlocking the Desktops, Special Music, and Tonko Art Gallery For Metal Slug Anthology on the PlayStation 4, GameFAQs has 27 guides and walkthroughs, 29 cheat codes and secrets, and 29 trophies. Then, load the saved game file and repeat as many times as desired.
Immediately after you defeat the final Boss (when the Boss is going up in flames), save the game, then quit to the main menu once the credits begin. You should get 5 tokens as you return to the menu, when you finally reach the menu just boot up the same game and load your save you'll be at the ending sequence again and you'll also earn another 5 tokens when you quit, repeat as many times as it takes to get everything in the gallery. Play Metal Slug 3 or Metal Slug 5 on the Hard difficulty setting. When you beat the last boss(When the boss is going up in flames or something like that) save the game very quickly, then wait until the credits start rolling and quit to the main menu.
To get tokens easily play through MS3 or MS5 on the hard difficulty with infinite credits if you need them.