Slide rules HOME page COLLECTION 20" RULES
Make Faber Castell, Germany
Model 4/98 Elektro

1. This rule has the same sale set as the 10 inch equivalent (1/98 Elektro)
2. Whilst one of the advantages of 20 inch rules ,compared to 10 inch rules, is increased accuracy, this could scarcely have been much of an advantage in this case since the errors in fabrication of the cables would have been larger than the 1:1000 accuracy of a 10 inch slide rule or the 1:2000 accuracy of a 20 inch slide rule.
3. There are windows on the back with hair lines on the stock for sin and tan (left) and log (right). The sine scale goes from 35' to 90 and the tan scale from 35' to 45.

Front view
2002-fabercastell-498-01.jpg (77647 bytes)

Detail - front left
2002-fabercastell-498-02.jpg (33647 bytes)

Detail - front right
2002-fabercastell-498-03.jpg (25897 bytes)

Detail - scales in well of stock
2002-fabercastell-498-04.jpg (29730 bytes)
Detail - back left
2002-fabercastell-498-05.jpg (29191 bytes)
Manufacturing date 6/1970 stamped on the back.
Length 20"
Material Plastic on wood
Scales A, [B, CI, C/ S, L, T] D
Gauge points p: 3.14: A,B,C,D
r' : 3438 : C,D
r" : 206255 : C,D
Cursor Glass with aluminium frame
Hair lines  
Documentation None
Condition Good