At first, this in the photographs looks like any aviation themed scale ruler. It has markings at 1:50,000 & 1:250,000. It has distances run at various speeds i.e. 420kt, 450kt & 480kts. There is also a conversion Metres to Feet scale, and a grid for accurate plotting on a 50k map.
However, one end is not at 90° to the main part of the ruler. It looks as if something has happened to the end, perhaps it was broken at some time, and was filed straight? But actually, this scale was manufactured as this shape.
So, what is it, and what is, or was, it for?
I realise there will be some Ppruners who will be familiar with it, so if they could hold of for a little while?
