1. The Shure Reactance Slide Rule with instructions and original envelope c1960
2. The Dodge Calculator for motor speeds c1960
3. The Ohmite Ohm’s Law Calculator c1960
4. The Durez Check Chart for specific gravities, and data on phenolic folding compounds c1980
5. The Set-up Master for Compound Angles, an engineering calculator c1947
Ask the Dealer
Fletcher Wallis sells objects and books relating to the history of science, medicine and technology from his unit at Admiral Vernon Arcade Portobello Road. He publishes books through Vernier Press, including Antique Medicine Chests, and Corkscrew Patents from 1795. He has been dealing for thirty five years.