Mathuradas Trikumji in his letter to Mahatma Gandhi says that Allopanisad is from the time of Atharvaveda (circa 1000 BC). R. Ananthakrishna Sastri in his article on the Theosophist, volume 19, Madras 1898, gives a statement that Allopanishad does not appear in the characterictic style of ordinary Upanishads. It was written in the style of old Rigveda verses.
Friedrich Otto Schrader in “A Descriptive Catalogue of the Sanskrit Manuscripts in the Adyar Library Vol. I. Upanisads”, page 136, states that some years ago, a palm-leaf MS of Allopaniṣad was in the Adyar Library, but it was rejected by the then librarian. In the North India according to Schrader, Allopaniṣad is not only reckoned to the Atharvaveda, but actually recited by the Brahmins at the Vasantotsava or any occasion when selected texts of the four Vedas have to be read in the house of a Dvija.
Written in “Vol 94 of The Collected Works of Mahatma Gandhi”, page 234, Mahātmā Gāndhī said: “But no one who belongs to Hinduism can have reason to complain. We have 108 Upanishads. One of them is the Allopanishad.”
Even though, Swami Vivekananda believes that Allopaniṣad must be a modern creation and not genuine, but in the book “From Colombo to Almora” published by Vyjayanti Press Madras in 1897, there is a statement in its Glossary that Allopaniṣad is one of the 108 Upanishads.
Allah Sūkta is written in situs “www.veda.harekrsna.cz/encyclopedia/upanisads.htm”: Ācamana vedānta, Āzrama, advaita vedānta, alla zakta (Allopaniṣad), Ārseya vedānta, Ātharvan-advitīya zakta, and so forth.
Viśva Bandhu Śāstri has mentioned 200 Upanishads in his “Vaidika Padānukrama Kośa” (Lahore edition, 1945). In these 200 Upanishads, “Allāh Upaniṣad” (Allaḥ Sūkta or Allopaniṣad) is mentioned on the 12th position.
The Kalyan Magazine, the 23rd edition, published in 1949 by Gita Press of Gorakhpur has mentioned 220 Upanishads in its special issue named “Upanishad-Ank”; and Allopaniṣad is mentioned on the 15th position.
Allopaniṣad is mentioned in “Upanisatsamgraha” or ‘The List of 188 Upanishads’, page 392-93, published in 1970 by Motilal Banarsidass Publishers Private Limited in New Delhi.
