English, late 19th century, in boxwood and brass, two slides with scales A, B, C and D, reversible to give Invd Line, WG scale (in this case indicating wire gauge), gauge points for unity and 5%, table of steel bar divisors, marked 'Designed and registered by C. Hoare'. Made only by Aston & Mander 25 Old Compton St Soho London, 62.5cm.