What is this Antique Brass Instrument on display at the Musical Instrument Museum in Brussels, Belgium? - Music: Practice & Theory Stack Exchange

Does anyone know what type of instrument this is? It looks like some type of Euphonium, but obviously very different.

The Brussels Musical Instrument Museum has some of the rarest instruments from around the world in its collection

Types of Musical Instruments, History & Examples - Lesson

Visiting the Musical Instruments Museum in Brussels - Bright Nomad

✓ MIM-Musical Instrument Museum - Data, Photos & Plans - WikiArquitectura

Various musical instrument hi-res stock photography and images - Page 5 - Alamy

What is this Antique Brass Instrument on display at the Musical Instrument Museum in Brussels, Belgium? - Music: Practice & Theory Stack Exchange

Visiting the Musical Instruments Museum in Brussels - Bright Nomad

Various musical instrument hi-res stock photography and images - Page 5 - Alamy

File:Antique brass instrument on display at the Musical Instrument Museum.jpg - Wikipedia