By its very nature, the Ibadi religious community, a form of Islam distinct from the Sunni and Shia denominations, was ruled by imams and had not an official polity style. There is a suggestion that in the 20th century negotiations the term Imāmat ‘Umān was used in some formal contexts.
Before the Canning Award of 2 Apr 1861 the dominions of the rulers of Muscat and Oman (and Zanzibar) had not the nature of a polity requiring a style. From 1861 sources begin referring to a "Sultanate of Muscat and Oman", but there seems to be no official documentation of this style.
(a) Masqaṭ wa ‘Umān
This is probably the most frequently used style. It is given official sanction by the legend on the postage stamps of the 1960s - the earliest that are not overprinted British or British-India stamps.
(b) al-Salṭana al-Sa‘īdiyya
This legend appears on coins of 1948, on which the ruler is styled Sulṭān Masqaṭ wa ‘Umān. The adjective Sa‘īdī - in analogy to the neighbour's Sa‘ūdī - appears to have acquired official status long before 1948.
There is no conclusive information on whether these two styles were ever combined into al-Salṭana Masqaṭ wa ‘Umān al-Sa‘īdiyya.
From 9 Aug 1970 the polity style is unambiguous - Salṭanat ‘Umān, but recent postage stamps carry the legends Dawlat ‘Umān, and State of Oman in English.
Emergence of Oman as Political Entity
Oman became the main home of the Ibadi community from the 8th century AD. The traditional head of this community was the imam (Arabic: Imām, in full: Imām al-Muslimīn, see Wilkinson (1987)). The imam was nominated by the (tribal) elders, and confirmed by the community.
Over the centuries imams have alternated with dynastic "kings" (malik), and Oman has been subjected to foreign occupation by Portugal and Iran, as well as strife with various Arabian tribal powers. The office of imam, while always formally elective, became dynastic with the Ya‘āriba (1624-1724, 1728-1749).
The liberation of Oman, and especially the city of Muscat, from the last Iranian occupation in 1748 signaled the supersession of the Ya‘āriba by the Āl Bū Sa‘īd tribe, with the election of Aḥmad ibn Sa‘īd as imam in 1749. His descendants, known as the Āl Bū Sa‘īd (family), became the rulers of Oman to this day. The site of the family was in the interior of Oman.
Imam Sa‘īd ibn Aḥmad was eclipsed by the conflicts among his brothers; among them, Qays ibn Aḥmad was encouraged by his brothers to claim the office of imam. Sa‘īd's son, Ḥamīd ibn Sa‘īd, occupied Muscat, ostensibly as his father's wakīl; when he died, Sulṭān ibn Aḥmad occupied Muscat, allegedly to support his brother Qays as imam; but he founded the polity later styled Masqaṭ wa ‘Umān, without claiming the office of imam. Imam Sa‘īd died in obscurity; the date of his death is variously given between 1790 and 1821.
Sulṭān ibn Aḥmad, and especially his son Sa‘īd ibn Sultān (d. 1856), extended the family's rule to a large stretch of the East African coast, ultimately moving the ruler's residence to Zanzibar. At the death of Sa‘īd ibn Sultān, his son Thuwaynī ibn Sa‘īd remained ruling in Oman, while his other son, Mājid ibn Sa‘īd, was in Zanzibar. Their conflict was adjudicated by the Earl Canning, the Viceroy and Governor-General of India, in the form of the "Canning Award" (2 Apr 1861)
This Award recognised Thuwaynī as "Sultan of Muscat and Oman" and Mājid as "Sultan of Zanzibar". From that date, the style sulṭān came into currency for the Āl Bū Sa‘īd rulers as used by foreigners - in particular by the British authorities in the United Kingdom and in India; these sought to establish their primacy, without (in Oman) the formal creation of a protectorate.
In 1868 there was a revival in Oman for the setting up of an Ibadi imam, and a collateral member of the Āl Bū Sa‘īd, ‘Azzān ibn Qays, was elected to that office and the sultan in Muscat was expelled. ‘Azzān was defeated and killed in 1871, by Turkī ibn Sa‘īd with the support of British forces, and the sultanate was re-established.
In the early 20th century the tribes in the interior of Oman again began to agitate for the imamate, and in 1913 a new Ibadi imam was elected, in defiance of the sultan. With British support, a modus vivendi was crafted with the Treaty of Al-Sib (25 Sep 1920), formally between the sultan and "tribes", but signed by the imam as Imām al-Muslimīn. The ambiguous arrangement collapsed in 1955, with the claim of sovereignty by the imam and consequent extension of the sultan's authority to the whole extent of Oman; there was an attempt at reviving the imamate in 1957, but it was defeated and its last embers were extinguished in 1959.
In 1970 sultan Sa‘īd ibn Taymūr was overthrown by his son, Qābūs ibn Sa‘īd, who re-organised the polity into the current Sultanate of Oman.
The Āl Bū Sa'īd family or clan, consisting of the descendants of Imām Aḥmad ibn Sa'īd, takes the name of the tribe to which its members belong.
The Omani descendants of Sayyid Sa'īd ibn Sulṭān (d. 1856) use the family or clan name Āl Sa'īd. The Zanzibari descendants apparently did not use it.