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2. This fully compensating 4 piston front action euphonium was the first of its species until the presentation of the Willson 2975 shortly after 1970. This prototype apparently never went into production

3. The small loop on the left side of the 4th piston is the stretch of tubing, where the bore expands from the one of the 3 first valve slides to the larger one of the 4th valve tubing. A similar loop can be found on the Besson 983 Eb tuba