Quartet 2 (unprotected) is an arcade version of Quartet 2 which may indicate a version of the game without copy protection, potentially allowing for unauthorized duplication or modification. This doesn't necessarily change the game's core mechanics or origin, but it signifies a different release variant. More context is needed to describe the history, gameplay, and developer.

Quartet 2 (unprotected)

Quartet (8751 315-5194)