Keuffel & Esser Rolling Ruler from 1950s

This is a pretty cool vintage measuring tool. K&E began making tools and scientific instruments in the late 1800's. I have this listed as being from the 1950s, but I suspect it's older than that. Anyway, it's a neat rolling ruler. If you want to measure a map or other drawing, you just roll this item along the line. It gives you the measurement in feet (up to 12), inches, and tenths. Multiply by the scale, and you have it. 

Marked made in Switzerland. Nice chrome or nickel plating. Appears to operate perfectly. 

Neat little tool to display or use.