This game was discovered inside a 'blue box' copy of the game. Most likely these are the very first releases of the games, and they were originally sold just as cassettes with inlay as seen here. As they became popular, they probably started making the blue box versions, sticking the remaining tapes with inlays inside the boxes. When these ran out, they just put the tapes (without inlay) in the blue boxes. Later on they switched to the red boxes and other publishers. That is the theory anyhow.