These are from the days when I had a complete Artillery plotting board with my Bedford MW. They came to me as a set. There is one Arc as used for map reading, one Grid and one 'Protractor Artillery Board Mk2 for Field, Medium and Heavy Arty'. Grid has pin holes where it has been pinned onto a plotting board. only ones of these I have ever seen.
Photo shows actual item.
Please Note:These items are from my own collection and so cannot be purchased through the web site; payment must be made direct by Paypal or Bank Transfer.