4.6 Years 1940-1949

Number of slide rules: 60.

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
c.1940	Hemmi	Triangulation
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	Simplified Flight Calculator Co.	Rhumb Line Distance and Course Computer
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	Goodyear	promo
1948	K&E	4083-3
c.1948	K&E	N9081-3
1948	Pickett	500
1948	Pickett	500
1948-1957	American Blueprint	Military
1948-49	Pickett	1000
1949	K&E	Mystery
1949	K&E	Mystery
1949	Otis King	Model L
1949-1958	Blundell Rules Limited	AL6
1949-51	Hemmi	159