| Name and Model Number | Martin’s Calculating Rule |
| Country of Origin | England |
| Date of Manufacture | 1918+ |
| Front Scales | Length 1’to 700’, Breadth 1”to 100”, Thickness 1/10” to 12”, Rate 1/8/- to 100/-, Amount £1 to £200 |
| Back Scales | Length 1’to 700’, Superficial Scale, Conversion Scale”, Rate 1d- to 60/-, Amount £1 to £200 |
| Scale Length | 72.5cm |
| Type of Rule | Slide Rule |
| Construction | Box with Brass Straps |
| Area of Use | Other |
| Comment | Costings calculations, primarily used in ship building.
Patent GB 135671 1918. Made by C.T. Cooper & Sons Ltd. |
| Rarity | RRR |
| Donor | Collection of Peter Fox |
| Match Number | 61 |
| Thumbnail |  |
| 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. |