Gurley termed this an Explorer's Level, and described it as "a small, light model designed
to meet the requirements of engineers for a compact and serviceable level for running
preliminary lines in exploration work where it is not convenient to operate a large instrument."
The design was introduced in 1914, and remained in production until 1934. The serial number
indicates that this example was made in 1915. It belonged to the United States Department of
Agriculture. New, it cost $110.
Ref: W. & L. E. Gurley, Manual of the Principal Instruments used in American Engineering
and Surveying (Troy, N.Y., 1920), p. 70.