1. Compared to other types of slide rules there were relatively few slide rules produced for hyperbolic logs - probably for the very good reason that few engineers or scientists needed them.

2. The complement of scales, one for hyperbolic tan (tanh) and one for 2 for hyperbolic sin (sinh) seems to be the standard. Outside of the range of values on this rule the values of tanh and sinh could be calculated without need of special scales.

3. For sinh the formula is: Sinh x = (e^x - e^-x) / 2. For small values of x (<0.1) sinh x = x. For large values of x (> 3) sinh x = e^x

Similarly the formula for tanh is:  Tanh x= (e^x - e^-x) / (e^x + e^-x) . For small values of x (<0.1) tanh x = x. For large values of x (> 3) tanh x = 1.

4. Note that the value of x is entered on the sinh or tanh scale and the value of sinh(x) or tanh(x) is read on the D scale.

My thanks to Mark Butterworth for providing the images of this rule. His web site is at http://www.priscus.co.uk .