Violin with metal tube

Violin with metal tub. The bottom and top sheets are glued together from two pieces of wood - each. A double line runs around the deck. On the upper deck there are two symmetrically 'f' shaped holes. The bridge's feet leg are made of raw wood. A metal tube that amplifies the sound is attached
to the back of the violin at a height of 10 cm from the upper fret. It is made of brass sheet.