According to Edith Reiter's 2014 book, this instrument was completed on 29 August 1906 and sold to a customer in Hungary.
Howe & Hurd (2004) describe heckelphone #22 as a model 36b. As of 2020, it is part of the collection of the musical instrument museum (Haus der Musik im Fruchtkasten) in Stuttgart, Germany, where it is catalogued as item no. 8.39 and has been on display since at least 2016.
Before becoming part of the collection at the museum, heckelphone #22 belonged to the Staatsoper Stuttgart. Earlier, it has been part of a large collection of historical wind instruments assembled by Dr. h.c. Karl Ventzke. According to Howe & Hurd (2004), it had previously belonged to the Budapest opera. Whether it passed through the hands (or collections) of other owners remains unclear.
An unofficial picture of heckelphone #22 can be found here.
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