Fearns Calculators Circular Slide Rule

This five inches circular slide rule with no specific name or code, was fabricated by the British company Fearns Calculators, by the early 1970's, and distributed in the United States and Canada by  Industrial Scientific Instruments Ltd., company based in Rouses Point NY. Fearns Calculators Ltd. specialized in the production of high quality engineering circular slide rules, one of them in this collection: the Fearns Tank Capacity Calculator. In the 1950's they were associated with M.H. Mears & Co, as Fearns, Mears  & Co. but in 1962 they dissolved the association continuing each with their own specialized and different range of calculators. Fearns Calculators appears to have ceased trading in the early 1980s.  

Fearns Calculators fabricated all plastic slide rules. This circular rule was fabricated with white plastic where color blue scales are engraved, and a plastic clear concentric disc with scales engraved in red and an indicator line in the middle, is screwed in the middle with the white pane, rotating around and over. A clear plastic indicator is also screwed to the plastic discs.  

The scales on this circular rule are: K, C ( D, A) B, spiral LL (~ 18.5 inches long), S, T on the front face, and unit conversion tables for Pressure,Weight, Length, Velocity, Area, Volume, Power-Energy, and specific weights on the back face. The simple logarithmic scales A, B, the double logarithmic C, D, and the triple logarithmic scale are not labeled. These scales set made the rule good for engineering work. 

The quality in its construction as well as the scales colors and design, make think that this rule could be displayed next to fine porcelains in a China cabinet, this slide rule is beautiful...

There is no serial number on this rule so is not possible to know the exact fabrication year:

I have not found the user manual or instructions sheet for this rule, but an experienced slide rule user user can easily figure out how to operate it. 

Here is a panoramic picture of this rule taken by the Australian Museum of Applied Science & Arts:

https://collection.maas.museum/object/74030