Original Item: Headspace in the Vickers medium machine gun is adjusted by adding or removing thin washers from the connecting rod. See Ian Skennerton, S.A.I.S. No. 8, .303 Vickers Medium Machine Gun, Plate G, items 15 ? 18. IMA has a few of the No. 1 (0.003 inch) and No. 2 (0.005 inch). British nomenclature is WASHER, ADJUSTING, NO. 1, .003-IN and WASHER, ADJUSTING, NO. 2, .005-IN. These are very rare, and IMA has only a very few. They are essential for the correct functioning of the Vickers. They are sold in packages of two.
This is type No. 1