1. Although the model name is only given as "Junior" it
is probably a Junior 2 as it has the trig scales on the back of the slide.
2. The fact that the rule does not have Thornton's patented differential trig scales may
date it before 1938.
3. The markers for the trig scales on the back of the rule were painted on and, as can be
seen in the detail, have now worn off. This may not have been a very accurate way of
marking in any case.
Front view
Detail - front left
Detail - back left
