Some games, like Metal Gear, uses cassettes to save your progress, and some other games, like Metal Gear 2: Solid Snake, uses the Konami Game Master 2 cheat cartridge. The thing that sucks about using cassettes is that while they can easily be emulated with curtain MSX emulators, some MSX2 computers(The one used to play Metal Gear)Don't have cassette input! So that means that you would have to start from the beginning to the end! That's what sucks about the saving system for Metal Gear. And for Metal Gear 2, you use the SRAM feature in the Konami Game Master 2 to save and load your progress. And that's how it goes! But too bad that MSX is dead now! But what the heck, it would be alright to play it sometime!
Coins can be used in vending machines.