A measuring magnifier is an instrument used to make very precise and very small measurements in a variety of areas. They can be used to accurately scale parts drawn on a blueprint or plan before they are transferred into real life. They can also be used to precisely measure text, look for forgeries in coins, notes or stamps or for scaling items on aerial photographs. With so many applications, it is unsuprising that examples have been used by the British military for many years. Today we are looking at a cased example that I think probably dates from around the time of the Second World War. The magnifier has an eyepiece at the top that can be screwed in or out to change focal length. Below this is a glass cylinder to let light in:

The base of the glass section has a red scale printed on it that can be seen when viewed through the eyepiece:

A /|\ mark and stores code is stamped into the metal of the eyepiece:

This is obviously quite a delicate little instrument, so it comes in its own metal carrying case:

This unscrews into two halves to allow the magnifier to be fitted inside:

As can be seen, the lid of the case is marked up with its contents and another /|\ mark. Above this can be seen a trademark for ‘W.O.&Co.’ I believe this is the mark of William Ottway and Company who manufactured optical and scientific instruments from the 1840s onwards and received a number of government contracts during World War II for items such as artillery sights and directors.