previous <<==>> next

CIRCULAR  SLIDE  RULE   ( 4" /  10 cm Diameter )
click the picture for flipping

SCIENTIFIC INSTRUMENTS CO., Berkeley, California / USA (1962)
                                                Made in Japan

S C A L E S   of the  CIRCULAR SLIDE RULE  » SCI  Model 120 «
Front Side                                          Back Side

                                             L     lgX
K     X3                                     DI    1/X
A     X2                                     D     X
D     X                outer circles         T1    tan(X)
-----------------------------------------    S1    sin(0.1X)
C     X                inner circles         T2    tan(0.1X)
CI    1/X                                    S2    sin(0.01X)
EI    sqrt( CI = 1/X <  ODD-No-Digits > )    T3    tan(0.01X)
      sqrt( CI = 1/X < EVEN-No-Digits > )    ST    arc(0.01X)

This Circular Slide Rule was the greatest bargain in the Bay
Area's huge ALAMEDA FLEA MARKET in May 2006 - it was free!
We got back our purchase price because it fall apart as the
seller put it in the bag...  It was dirty, had two broken
cursors and a missing center screw.
The cursors are now made of PVC and reinforced at the ends
with slices made from a cat food can. The hairlines are made
with a sharp » X-ACTO « and colored with a permanent marker.

                   Historical Remarks ...
*************************************************************            12/14/06