Date: 1937. Owned by Pieter Vos
At first the 20K was called the "Sousaphone Grand", then renamed "Artist". This change probably occured in 1955. The 20K had a 0.734" bore, which is a #10½
What Conn said in 1938:
The 20K with short action valves is the latest addition to Conn sousaphones, and promises to be the most popular of all. For many years, the 38K sousaphone has been recognized as the finest sousaphone on the market. Its big, flashing 26-inch bell has towered above the heads of some of the best bass players in the world and its majestic, deep-intoned voice has stirred thousands. Now, with the new and revolutionary short action valves, this new 20K model is unquestionably the last word in sousaphones. [...] They cut the stroke by 33 per cent and give almost cornet-like action. This instrument is made by the exclusive Conn Hydraulic Expansion Process, the scale is smooth and flexible, the intonation accurate, the response quick and easy, the response quick and easy, and the tone -an outstanding feature on Conn basses- is big , solid and rich. Bell adjustable and detachable. Mouthpipe equipped with swivel, cruved bit for obtaining comfortable playing position.
What Conn said in 1959:
World's finest large bore BBb sousaphone. Crysteel short action valves are fast, positive with the pin guide construction. Balanced taper from mouthpiece to bell is protected by the hydraulic expansion precision process. 26" bell is adjustable and detachable. Features: large bore full tone, clickless Crysteel valves with pin guides, short action valves 1/3 shorter than standard for large bore, off-set valve stems for easy finger position. High polished brass with clear lacquer finish.
Also available: Satin silver finish with gold bell. Upright bell only, highly polished brass clear lacquer finish. Upright bell only, satin silver finish with gold bell.