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Fearns Calculators: A13 Circular Slide Rule

Fearns Calculators A13

Details of: Fearns Calculators - A13 Circular Slide Rule

Type? A generic name (e.g. Rietz) or function/use for specialist models (e.g. Meteorology) for grouping similar models across makers. If not “standard” 25cm linear length, preceded by the form (i.e. Demonstration, Desktop, Pocket, Waistcoat, Keyring, Lilliput or Book) + if needed, qualification to distinguish between versions (e.g. early or late). Log-log
Sort? L/C/D/T/W/X where L=Linear, C=circular, D=Drum, T=tubular, W=watch, X=miscellaneous (i.e. the rest) C
Construction? Basic construction form of the body i.e. Closed/solid frame or Open frame or Duplex or Other Other/simplex
Material? Basic description: ivory/bone/wood/bakelite/plastic/metal/cardboard or combinations e.g. wood/veneered, wood/painted, etc plastic
Length? Mostly the linear length of the D scale (in cm or inches) excluding any extensions. For circular/watch slide rules it is the diameter but for helical/tubular/drum slide rules it is the overall scale length. For other calculating aids it is the physical length. Ø 5"
Scales front? Standard (not maker’s) symbols for scales on front face e.g. A = X² (1-100) but § = generic symbol (signum sectiōnis) for any non-standard scale + scales between solidi / / are on the slide(s) whereas scales after vertical line | or after reversed solidus \ are on a straight or bevelled top or bottom side edge K,D / C,A / B,LL,S,T
Scales back? Standard (not maker’s) symbols for scales on back face e.g. S = sine (5° to 90° & 85° to 0°) or sin(x) but § = generic symbol (signum sectiōnis) for any non-standard scale + scales between solidi / / are on the back of slide(s) but scales listed after / / - notation are on another surface e.g. back of stock or inside a lid
Cursor type? Basic description (incl. material) + no. of hairlines, etc on any cursor(s) or alternative to a cursor - e.g. a stylus plastic delta wing - 1 hairline
Condition? Cn where n = 0-6  condition/quality scale where 0 = brand new in box & 6 = broken   C2
Date? YYYY for year(s) of production or an approximation/range of years 1970s
Extras? Basic description of any accessories - e.g. case or stand + where relevant, an accreditation for image, etc black plastic wallet with "Circular Slide rule" in gold - image courtesy of Rod Lovett
Instructions? Details like “on back of rule” and/or language of instruction sheet/booklet - generic or instructions for common layouts usually not listed leaflet in English (n.b. office address in Newcastle-upon-Tyne)
Booklet (PDF)? Downloadable .PDF copy of unusual or uncommon model specific instructions download
Comments ? Any special or noteworthy traits + significant use-related facts + pertinent details of scales/tables in well of stock + any significant tables, etc on the back of the stock

LL scale to base 10 - tables of conversion factors on back

In-Out? MM-YYYY / MM-YYYY of the date added/left the collection or <YYYY if exact MM-YYYY no longer known <2005

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