細節
An Abney level with compass,
in oxidised brass with prismatic compass sight, folding foresight, protractor with vernier, scale magnifier and level visible in main sight and folding staff-socket -- 5in. (12.5cm.) long
in oxidised brass with prismatic compass sight, folding foresight, protractor with vernier, scale magnifier and level visible in main sight and folding staff-socket -- 5in. (12.5cm.) long