1. This is a deceptively simple looking rule but it has a very full complement of scales including trig, log-log and hyperbolic functions.
2. The rule was made by Eckel, presumably part of Pickett and Eckel, so my estimate of 1950 may be late as Pickett and Eckel were formed before that date.
3. A unique feature on this rule is a lock on the cursor which enables it to be rotated with the rotor. (The rotor is the equivalent of the slide on a straight slide rule).
4. I give the instructions for the rule here.
5. If you have any information on this rule I'd be pleased to hear from you (sliderules@clara.co.uk)

My thanks to John Fahey for providing the images of the rule and of the instructions.