There's a ton of different requintos, most of them guitars, most of them different by origin and string number etc. The one we need is the Mexican 6-string one, which is different from the (also Mexican) 4/5 stringed requinto jarocho.
disambiguation: "small 6-string guitar used in Mexican trio romántico music"
description: "The Mexican requinto is a small 6 string guitar, tuned a fourth higher than a classical guitar, and usually played as one of the three instruments in trio romántico music"
subtype of guitar, or even of classical guitar?