That is an very nice example of a MkII helmet with a direct family connection, even the chin strap and interior look great. On the interior, near the seam for the rim should be the stampings for manufacturer, batch numbers and year of manufacture, look for AG, C.L/C or G.S.W. (Aluminum Goods-Canadian Lamp Company or General Steelwares), DP&H is for Department of Pensions and Health and was a mild steel helmet used for ARP purposes.