4.6 Years 1940-1949

Number of slide rules: 56.

Reciprocal log-log scales began to be added to some of the advanced slide rules along with the normal log-log scales.

Some notable technical developments: World War II, the synchrotron was invented, nuclear power, first transistor, first electronic digital computer.

Year Maker Model
c.1940 Dietzgen 1745
c.1940 Gilson Midget
c.1940 Hemmi 40
1940 K&E 4110
c.1940 Lawrence 10-B
c.1940 Sandish Spring Calculator
c.1940 noID Engraving Rule
1941 Baetzmann Spring Calculator
c.1941 Charvoz-Roos SR-104
c.1941 Charvoz-Roos SR-109
1941 Gilson Binary
1941 K&E N4041
1941-1952 Dietzgen 1735
1942 Charvoz-Roos SR-109
1942 Dietzgen 1767-P
1942 K&E 4058D
1942 K&E 4058D
c.1942 Lawrence 10-B
1942 Sillcocks-Miller M1 Slide Rule No. 547
1943 Felsenthal AN 5837-1
1943 Fowler Long-Scale
1943 Unique Navigational
1944 Felsenthal D-4
1944 Hemmi Byoutou
1944 K&E 4097D
1944 K&E 4098A
1944 K&E N4133
1944-45 Charvoz-Roos PSR-105
c.1945 Acu-Rule Acu-Math 90A
1945 Charvoz-Roos SR-108
c.1945 Charvoz-Roos Power Trig
1945 Thornton P.I.C. 101
c.1945 Unique 5L/L
1945-1955 HH Universum
1945-46 Pickett 1
1946 Acu-Rule Arel G-W Photo
1946 K&E 4054
1946 K&E 4139
c.1946 Lawrence 10-D
c.1946 Lawrence 10-N
1946-47 Pickett 2
c.1947 Bruning 2401
1947 Faber-Castell 1/87m
1947-49 Hemmi 32
1947-49 Pickett 3
1947-49 Pickett 4
1948 K&E 4083-3
c.1948 K&E 9071-3
c.1948 K&E N9081-3
1948 Pickett 500
1948 Pickett 500
1948-1957 American Blueprint Military
1948-49 Pickett 1000
1949 Otis King Model L
1949-1958 Blundell Rules Limited AL6
1949-51 Hemmi 159