This is a special metal & enamel pin set made for Sonic 3. It was released in Japan (somehow) but then re-purposed as what is likely a 'booth gift' or 'booth swag' for attendees of a convention (E3?) in the USA when Sonic 3 came out. They likely added an extra pin (standing Sonic in the bottom left) to make the set slightly different / exclusive for this event. Otherwise, the 3 pins are exactly the same as the Japan edition ones with the "3" logo, wierd tall/narrow/wrong eyes Knuckles, and Sonic doing the "3" pose with his fingers...but what is his other hand doing? Pointing? Yes that tiny bit at the bottom is his far off foot. Both character pins here are rather oddly done / odd art choices. It's an interesting little set though, uncommon because it was only brought over in limited quantities for some event.