British currency in the Middle East already risen in value against the pound sterling as a result of sterling's devaluation in 1967, and so the new Omani rial was not equal in value to the dinars in the nearby territories. The currency units that are used in Israel, Jordan, Iraq, Kuwait, Bahrain, Oman, and the Yemen are all descended from the pound sterling unit, while the currency units that are used in Saudi Arabia, Qatar, and the United Arab Emirates are all descended from the Maria Theresa Thaler. This largely explains the factor of ten difference in value on average between Bahrain, Kuwait and Oman on
Manx pound and there is no guarantee of convertibility beyond that given by the Manx authorities. However, the requirement in the island's Currency Act 1992 for the Isle of Man Treasury to exchange Manx Pound banknotes on demand for Bank of England notes in practice restricts the issue of unbacked currency, and the aggregate total of notes issued must be pre-approved by Tynwald. ISO 4217 does not include a separate currency code for the Manx pound, but where code distinct from GBP is desired, "IMP" is generally used. UK notes and coins (whether from banks in England, Scotland, or Northern Ireland) are