This is not a guiter. It is a Tres and, if played properly, it sounds more vibrant than reqular Spanish guitar.
The Tres is a 3-course, 6-string chordophone which was created in Cuba. A later adaptation, the Puerto Rican tres, is a 3-course, 9-string instrument.
The Cuban tres has three courses (groups) of two strings each for a total of six strings. From the low pitch to the highest, the principal tuning is in C Major: G, C, E.
A Book to learn the Cuban Tres - ACERCA DEL TRES,EL SON Y EL TUMBAO by Efrain Rios in www.habanapopular.com and more in espanol.groups.yahoo.com/group/eltrescubano/