According to Edith Reiter's 2014 book this instrument was completed on 1 August 1946 and originally sold to a buyer in the USA.
Howe & Hurd (2004) describe heckelphone #4720 as a model 36i; it was later modified into a variant of model 36k with a bridge from 4 to activate the side plate for Bb and C.
As of 2004, heckelphone #4720 is reported to be located in Stockholm, Sweden, and to belong to the Swedish Radio Symphony Orchestra.
The history of heckelphone #4720 remains largely unclear.