This rule was cheaply made but has survived for around 80 years.
1. The slide is a most unusual one, being all metal (tin plate) with painted scales.
2. The cursor consists of a folded strip of plastic held in place by a metal clip.
3. The patent was issued in 1919, so the rule was probably made during the 1920s.
4. The rule has sin, tan and log scale on the reverse face. There is a small mark on the reverse stock for the log scale.
5. The rule is provided with two slides. The second one including scales for electrical calculations.
6. The only gauge mark is 1146 (Gunner's mark) suggesting an artillery use.
7. A copy of the original Patent Specification can be found here. (Thanks to Peter Hopp for obtaining the Patent and providing me with a copy.)
8. A copy of instructions in a contemporary book (Slide Rules and How to Use Them by Thos. Jackson) can be found here. (Thanks to Jim Bready for providing the scans of the spare slides and instructions.)
9. I have another US made Richardson rule which also is made of tin plate.
Front view
Front left
Showing gauge point of 1146
Cursor
Plastic with metal clip
Rear view showing trig and log
scales
Front and back - slide 1
The A scale is displaced by 0.89 (app)