In 1991, when unpacking a removal box, I came across the long-forgotten slide rule from my student days. I was intrigued - when and why did they become obsolete? A bizarre tongue-in-cheek idea struck me: “As an (ex)computer man I had to collect analogue slide rules!”

Slide rules do not wear out or get easily damaged and unlike modern-day calculators, they do not need batteries! Most slide rules have a pair of Log x (C/D) scales but they can come in many shapes and sizes:

• Linear - by far the most common
• Circular or disc form
• Drum or cylinder form
• Tubular or spiral form
• Watch form (pocket or wristwatch)

My collection is mostly made up of slide rules but various slide charts, novel calculating aids, a hybrid or two and even the odd electronic calculator makes an appearance. For new or budding collectors the Reference Manual published by the Oughtred Society succinctly covers the basics and much more. Or try a surprising read: An Easy Introduction to the Slide Rule by Isaac Asimov (yes, the SF writer). For cleaning and restoration tips Eric Marcotte’s or Tom Dilatush’s web pages are full of good ideas and helpful tips. There were many makers but if you find you are stuck pinning down the maker of an unbranded/unmarked item try working through my Solving Mysteries crib sheet. 

The niche sections of my collection are my many ♫ acoustic ♫ slide rules (yes, they exist!) and oversized desktop models. But also anything quirky like a slide chart for Church bells. Nowadays my focus is on adding models missing from my collection by the two Dutch makers: ALRO and Systeem Matthijssen. Over the years my collection has grown to 1800+ Slide Rules, 200+ Slide Charts, 40+ Ready Reckoners, 15+ Slide Adders, 30+ Mechanical Calculators and a handful of Electronic Calculators. Every month or so I try to upload a new batch - so far, about 90% is online. 

Do try one of the adjacent SEARCH options or the BROWSE ALL function to learn about items of possible interest.