For your consideration, here is a Vari-Vue 6 Inch Advertising Ruler, for Yates Products, of Glendale, California.  It has the old style letter prefix phone numbers:  CHapman 5-3678.  The view switches between fractions and the decimal equivalents.  It has some wear, spots and some green paint on it.  It will be mailed in a box for protection.  Item pictured is the actual item up for sale, and comes from a non-smoking household.  (416.977as-.5ob)