| Name and Model Number | Noble’s double rule |
| Country of Origin | UK |
| Date of Manufacture | c1895 |
| Front Scales | Routledge variant |
| Back Scales | Engineering and steel measure |
| Scale Length | 11” |
| Type of Rule | Other |
| Construction | Boxwood & brass |
| Area of Use | Other |
| Comment | 2-foot, 2-fold used in engineering.
Noble’s double slide rule is one of very few 2-foot, 2-fold slide rules to have a slide on both legs of the rule, one each side. Noble’s rules are unusual in using a 5 – 50 ‘D’ scale. This particular example is unusual in having extra width on one of the legs, so that additional scales could be included, it may also be a prototype as it carries Noble’s name under one slide. There appears to be several variants of the double rule, mostly with equal width legs as the majority of the 2-2 rules. |
| Rarity | RRRR |
| Donor | Collection of an English gentleman |
| Match Number | 54 |
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| RR | = Rare -- 1 of 25 collectors has one; it may take a year to find an example in the marketplace. |
| RRR | = Very rare -- only very few known to collectors; may take several years before one comes up for sale. |
| RRRR | = Extremely rare -- a museum piece; unlikely that an example will ever come up for sale. |