The last No4 Parts list illustrates breeching up washers for the No4 Mk2's. I have just spoken about this to Sgt Rxxx Sxxx and he's confirmed that many from the RAF ACF's and CCF's (Cadet forces) that went through the main workshops had them. This indicates to me that they will be the LATER Mk2's (maybe the UF's). The breeching up washers were not codified (didn't have part numbers) so they had to apply for them. They had them in stock as they used the L39/42's as required or for an odd size, machined up