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1815-1910 Antique brass surveyor’s Wye level. The Wye level, or Y -level, became the premier surveying instrument of the nineteenth and early twentieth centuries due to its precision and ease with which its optical alignment could be verified and adjusted in the field. Named for the Y- shaped supports that cradle the telescope, this design allowed the surveyor to lift the telescope, rotate it end for end, and quickly check for collimating errors.
American instrument makers such as W. & L.E. Hurley , Keuffel & Esser,and Buff & Buff established high manufacturing standards, producing robust brass and bronze instruments that withstood rigorous field conditions in civil engineering and railroad conditions These instruments were typically finished with a dark chemical dip to reduce blinding sun glares during field observations while leaving polished brass highlights on the working environment threads of the screw heads.