A rare Rabone rule no 56 with an attached Vernier scale. The top scale on the rule is marked in tenths of an inch and the lower scale is in twentieths and has the sliding Vernier scale.
We have not seen one like this before and can't find any reference to it online. It predates 1963 as Rabone and Chesterman merged at that date to form Rabone Chesterman.
In good usable condition, the vernier fits firmly and slides smoothly, also an interesting collectable.