English, c.1921-1923, number 7870 (no preceeding letter) in nickel plate with white on black scales, cursor a single tube with index marks in the form of arrows, no address on scales, in fitted velvet and silk lined case, covered in black Morocco leather with gilt decoration, silk with label 'Otis King's Patent Calculator Patentees and Sole Manufacturers Carbic Limited, 51, Holborn Viaduct, London EC1', case 18cm