On what is the earliest of the extant Papalini bass clarinets (D-Leipzig, ca. 1820), the omega section has a single coil, unlike all later examples, which have a double coil. It has seven round finger holes, one thumb hole, five keys with square heads with the Ab/Eb key positioned for R4, the F#/C# and E/B keys positioned for L4 as on the soprano clarinet, and a resonance hole on the bell base. There are no double finger holes as found on later examples. Stamped on the omega section is “N.PAPALINI/CHIARAVALLE.” A photo of this bass clarinet in 1901 shows a second barrel section and mouthpiece; this appears to be replaced with a single-coil omega section above the barrel in a photo for the Heyer Collection catalog of 1913.

Rice, From the clarinet d’amour to the contra bass, 284.