The unique existential quantifer is the symbol ∃!. For example,
means "there exists an unique x such that x-2 = 4".
History of the Quantifer
TODO
See Existential quantification for details.
... Central Museum & Art Gallery[?] Norfolk Bressingham Steam Museum[?] East Anglia Railway Museum[?] Strumpshaw Hall Steam Museum[?] Toad Hole Museum[?], How ...