Sackbut - or baroque trombone. 

Sackbut is an old English name for trombone, which derives from the old French verbs for pushing and pulling; the movement creating different tones on the instrument. The trombone was invented around 1450, and the instrument's unique construction remains almost unchanged since then. Today the word sackbut is used to describe the trombones that are copies of instruments from the renaissance period, and these instruments have thinner tubes and smaller bells than the modern trombones.

 

Different sizes of sackbuts, from left to right: alto, three tenors, and a bass.