Technical description: Brass. Windway runs mouthpipe - 4 - m.t.s. - 1 - 2 - 3 - bell. The main tuning-slide is long enough to lower pitch to B♭ and is graduated at positions for B♮ and B♭. Music card-holder fitting, no water-key. The bore expands very rapidly just beyond the valves.The bore profile approaches that of a euphonium and the instrument may have been intended to be used as a bass saxhorn, possibly in a marching band.
Valve type: 4 Stölzel valves with spring inside hollow stem; alignment by unequal lugs on spring anchor plate.
Signature / Marks: Inscribed on bell "AUGTE. COURTOIS AINE / BREVETÉ S.G.D.G / PARIS"; on lower side of valve casings "548"; on inner main tuning-slide adjacent to graduations "SI" and "SIB".
Performance characteristics: Good response; tuning fairly good when in C, but flat fifth natural note of open tube when slide drawn for B♭, closer to D♭⁴ than D⁴.
Usable pitch: Diapason Normale, plays c 20 cents below A⁴ = 440 Hz.