I bought this book to help identify vintage slide rules and I was sorely disappointed. There are no pictures. There is little information what the rules look like, what they're made of, and when they were made. I recently picked up 30 rules from various manufacturers and many of them were not listed in the book. The book only provides date ranges rules were made, no specifics on determining the exact age. For a particular manufacturer, like Sun Hemmi, the book does NOT provide the simple method of determining rules made from 1950 on (the 2 letter code).