According to Edith Reiter's 2014 book, this instrument was completed on 25 January 1909 and sold to a customer in Austria.
Howe & Hurd (2004) describe heckelphone #42 as a model 36b with a muting bell. As of 2016, it was located in Vienna, Austria, and belonged to the Wiener Staatsoper, who acquired it directly from Heckel. The instrument was likely used in the first performance of Elektra in Vienna on 24 March 1909.