In 1991, when unpacking a removal box, I came across the long-forgotten slide rule from my student days. I was intrigued - when did they become obsolete? Soon a bizarre tongue-in-cheek idea struck me: “What else could an (ex)computer man collect but 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 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 (pocket or wristwatch)

Most items online are slide rules but various slide charts, novel calculating aids, a hybrid or two and even the odd electronic calculator makes an appearance. For fledgling or existing slide rule collectors the Reference Manual published by the Oughtred Society succinctly covers the basics and much more. Or try 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 webpages have good ideas and helpful tips.

The slide rules in my collection come from many makers. But if you are trying to find the maker of an unbranded/unmarked slide rule try working through my Solving Slide Rule Mysteries crib sheet. The niche sections of my collection are my ♫ acoustic ♫ (yes, they exist!) and my oversized desktop slide rules but also quirky models - e.g. for Church bells. These days my focus is on adding models from the Dutch slide rule makers: ALRO and Systeem Matthijssen. My entire collection has grown to 2000+ 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, roughly two-thirds are online. 

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