A rare 19th C. steel right angle sliding rule by E.V.Trigt in Delft in its original mahogany case.

A steel sliding rule in a mahogany case. Overall length of the rule 57,5 cm. The rule has a double vernier and at its end has the makers signature: "E.v.Trigt Delft". It is kept in a nicely made dovetailed mahogany case with three brass hooks and a green textile lining. The unusual feature is that there are no measurement markings on either side. Also the verniers are blank. Possibly one side was reserved for centimeters and the other for inches. Most likely the rule was made around 1820 when the meter was introduced in the Low Countries.