Buescher sopranino in C

C soprano = about 22", sopranino in Eb = about 18".
I suspect it is a C soprano.

Not just Bueschers as almost all conform. The difference would be if the horn did not have a low Bb, only to B where a Bb horn could be mistaken for a C soprano. Ebay usually has Bb sopranos called sopranino so just beware. An easy way to spot a C is the lever for the low C is very close or over the pad cup. King Bb sopranos have two low C pads whereas the C sopranos have only one. Most Holtons in C go up to high F and most others only go to Eb (except a few rare Bueschers).