British Thornton  10" Slide Rule (1967) No. P271 LOG LOG

Sale Results at Auction


AG Thornton Manchester was founded by Alexander George Thornton in 1880. In 1901 The Precision Instrument Co was taken over, for their slide rules. Plastic models where introduced in the 1960s. In 1967 the firm became British Thornton. It was merged with ESF at Burley in 1992.

It had become one of the largest manufacturers of drawing instruments and slide rules in Britain.


The No 271 Log Log open frame, simplex plastic slide rule has scales: LL2,LL3,L,A{B,C1,SD,TD,C}D,S,ST,T. The is a British Thornton post 1967, and is of heavier construction than the earlier 1963 version. It is similar to the P221. It has a black plastic case; some had a hard plastic case.  

In 1965 I learned the power of logarithms, using logarithmic and trigonometrical tables to 4 decimal places. In 1967 I developed a talent for technical drawing and had British Thornton set squares and a beautiful adjustable set square. It was at this time I discovered the British Thornton slide rule.

Many slide rules in use had chipped ends. The No P271 has protective ends and a spring loaded cursor that would lock in place allowing intermediate calculations to be recorded. Although showing signs of plastic discoloration it has done better than most white plastic items purchased even 5 years ago.

I continued to use the 4 and 5 figure tables through my CSE, GCE and A Level Mathematics and Physics examinations in 1972. Most of my experiments in physics (at the rate of 3 to 9 per week) had the results calculated using the slide rule, accurate to 3 decimal places. My lab partners provided validation with results using tables. The speed and accuracy of the slide rule allowed me to have three active experiments on the go and to write up the results during the time that others where still packing up to go.

Aluminium Pickett-brand slide rules were carried on five Apollo space missions, including to the moon, according to advertising on Pickett's N600 slide rule boxes.

Sale Results at auction

On eBay plastic Thornton slide rules sell for for anything from 0.99GBP to 12GBP

2010/01/17 0.99GBP
2010/01/17 5.50GBP
2010/01/23 8GBP
2010/02/14 6.50GBP


AG Thornton

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How to Use a slide rule

How to make a slide ruler How to make a slide ruler. Click on the image (left) to view full size. Print off to make a slide ruler.

Last updated 21st November 2010