Metallophone is a generic name - for example, glock and vibes are also "metallophones", in the simple sense that they all have metallic note bars. They have been around for centuries, and feature in traditional music from Bali and Java.
Typically, we supply the Diatonic model, which comes not only with the "white" notes which make up the C major scale, but also some extra notes (Bb and two F#) which can be simply interchanged with the B and F notes to cope with songs in other popular keys. If you wish to upgrade to a full chromatic version, the chromatic half is supplied with the missing C#, Eb and Ab notes to complete the entire scale. Do please ask the Advisory Team if you need clarification.