|Name and Model Number||Aston & Mander|
|Country of Origin||UK|
|Date of Manufacture|
|Front Scales||Tonnage/Gauge Points, Extreme Breadth/ Length for Tonnage|
|Type of Rule||Slide Rule|
|Area of Use||Other|
|Comment||Naval architects tonnage calculator.
Carries the name G L Watson & Co. Naval architects and surveyors, Glasgow, Scotland on the back.
|Donor||Collection of Colin Barnes|
|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.|