The I.C.I. sticker would make it post 1930 and pre 1963. I have a 1935 Eley Kynoch catalogue and a circa 1960 catalogue and both list the .300 Rook but only mention the bullet weight at 80 grns. and type. The older catalogue lists it as available in both black powder and smokeless though sadly no mention of the primer type. I shoot .300 Rook and seek out old boxes of ammo. I have an identical box but no mention of date. My other boxes are much older. I would suspect your box to be around the late '50's to early 60's with the red & yellow box although I can't find a definitive date for the box design change. Lagopus.....
