Most commonwealth Banknote collectors I have met have confirmed that the U overprint in a circle on the 1 Dollar East Caribbean States either does not exist or not in their collection. The U overprint is scarce primarily due to the limited issue size issued  with one or very few prefixes

Though there are few known pieces this is an extremely scarce variety and a great addition to any collection (If you manage to find one)

Denomination : 1$

Year of Issue : 1965

Member Countries at the Back of note: Third Issue includes Grenada but not Barbados

Prefixes known : B92 (If in any other prefix please feel free to email)

Rarity Score : 9

Factors considered: Issue Size, Popularity/awareness/knowledge of the variety that drives demand, Denomination