This is a modern reproduction of an early slide trombone or "Sackbut". The Sackbut is a brass instrument from the Renaissance and Baroque eras, and is a direct ancestor of the modern trombone. The name is derived from the Middle French sacquer and bouter ("push" and "pull") and the term survives in numerous English spelling variations including sacbutt, sagbut, shagbolt and shakbusshe. In France, the instrument was called sacqueboute; in Germany, Posaune, and in Italy, trombone. Renaissance wind band pitch was typically set at A= 466 Hz, approximately one half step higher than modern pitch. The tenors that survive are more or less pitched in Bb at A=450 approximately.  A renaissance saqueboute recently discovered in France was made in Kopenhagen c.1442 by an English maker!!

Early true hand slide instruments (Trombones or Sackbuts) , had very small bells, limited flares and a small mouthpiece and bore. The sackbut's sound is characterized by a more delicate, vocal timbre than the modern instrument. Its dynamic flexibility lends itself to a vocal style of playing. These instruments were usually paired with Cornetts and corresponding voices in a choir.   Listen here to a Montiverdi piece played by the English Cornett and Sackbut Ensemble

While a sackbut does not fit preceisely into my collection of valved horns, but it does represent one of the earliest forms of brass instruments and thus certainly belongs in any historical brass presentation. This sackbut has the dimensions of a small tenor trombone- but with a bell of 3-3/4   inches (9.5 cm) diameter. the mouthpiece receiver is about .375 inches. 

Böhm & Meinl  was a long established brass instrument company in Geretsried, Germany.  Walter Nirschl,  a sixth-generation builder of musical instruments, purchased the Böhm & Meinl Company in 1992  which is now known as B&M Symphonic (the inscription on the bell). This horn was originally sold by the dealer Max Hieber of Munchen. 

Scroll down to see a historic print depicting Sackbuts and Cornetti and Natural Trumpets used in 17th and 18th century music.