Keuffel & Esser Engineer's Railroad Y Level, No. 5012½

A precision surveying instrument by Keuffel & Esser Co. of New York, the extra-fine Engineer's Railroad Y Level, Model No. 5012½, serial number 3984. The mounting plate carries the patent dates Dec. 3. 89, Aug. 12. 90, May 26. 91, and Oct. 3. 91. It dates to the 1910s.

The Y, or wye, design rests the telescope on two uniformly turned collars set in vertical supports, allowing quick and accurate leveling. The focusing knob sits at the top and works smoothly; the 32X telescope has clear, bright optics and brings the cross-wires into sharp focus. Carefully cut leveling screws and a stable leveling plate account for the rest of the instrument's precision.

It is built from high-quality bronze bell-metal alloys and brass, with a mahogany base and case. The instrument stands 8 inches high; the telescope measures 20 inches, extending to 22 inches, and to 24 inches with the sunshade in place. A similar model is exhibited in the Physical Sciences Collection at the Smithsonian's National Museum of American History, Washington, D.C.

Should the level be put back into surveying use, for which it is suited, it should first be serviced and adjusted by a professional experienced with surveying instruments.