According to Edith Reiter's 2014 book, this instrument was completed on 8 April 1911 and sold to a customer in the UK.
Howe & Hurd (2004) describe heckelphone #50 as a model 36i; a thumbplate Bb/C mechanism was added after purchase, and in 2003, it was modified by Keith Bowen to the keywork of a model 36k.
As of 2020, this instrument was reported to belong to a collector in San Diego (CA), USA, who acquired it from noted heckelphone specialist, Peter Hurd, sometime after 2004. It was sold at action by Sotheby's in London, UK, in 1979, to a dealer for musical instruments in Zurich, Switzerland. Prior to that, it used to belong to oboist James MacGillivray of London, UK, who purchased it from bassoonist Alfred Penn of London, UK, in 1938. Whether Penn purchased the instrument directly from Heckel remains unclear.
Heckelphone #50 is reported to have been used at the Royal Opera House in Covent Garden, London, UK, and has been played and recorded in the Hoffnung music festival concert in 1956, where it was used for Malcolm Arnold's Annie Laurie Variations.