We just got in this great vintage surveyors rod. We LOVE the graphic pop it adds to any interior and the nice industrial edge it provides. We understand this is known as a Philadelphia rod.
The two piece telescoping pole would be sighted by the surveyor to obtain the needed measurement. The "target, shown in detail below, slides up or down until it matches the surveyors line of sight. 
Here are some vintage images of surveyor rods in use:
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