Dachau KZ Blog states that the Obersdorf sub-camp was located in the community of Bad Hindelang in the Allgäu. It was established on the 20th March and existed until April 1945, consisting of only one prisoner who worked for Rudolf Hess's wife, Ilse Hess, in her house following the flight of her husband to England, after which he was detained there. Ilse Hess owned a small form in the village and probably requested assistance from the Labour Exchange (Arbeitsamt). The prisoner sent to assist her was Friedrich (Fred) Georg Frey who was a Jehovah's Witness from Röt near Baiersbronn who had been arrested in 1937 and detained in Dachau. On 18th February 1940 he was transferred to Mauthausen. He was finally liberated from Dachau in 1945.

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Frey performed tasks such as gardening and the care and milking of ewes and Iceland ponies. He was ordered not to associate with the family, but Hess disobeyed this order and allowed him to sleep in the house and eat with the family at evening meals and dinners, rather than confining him to the stables. He was also allowed to wear civilian clothes rather than his prisoner uniform. Although Frey did not mention how he had been treated while living at Ilse Hess's house, he did say he had been treated fairly miserably at other locations, causing permanent damage to his health. His labour in the Hess house ended on 20th April 1945 and from there he travelled to his own home. Not much else is known about Frey after the war. Ilse Hess moved to Bremen where she died in 1995. Her house in Bad Hindelang is owned by her daughter-in-law.