La Fay Helice a Calcul No. 1 and No. 2
France, 1931, scale lengths 85 cm and 250 cm, paper scales on cardboard tube.
On No. 2 the spiral scale winds 50 times around a 4 cm diameter tube to give a total scale length of approximately 2.5 m and a precision of 4 digits.
A sliding celluloid sleeve and three celluloid cursors facilitate the calculation.
Can be used for multiplication, division, and logarithms.
Advertising for this instrument appeared as late as 1945.